The irradiated GaAs sample was provided by Yang Cui of the University of Illinois at Chicago. This work was supported under Contract No. DE-AC02-06CH11357 between UChicago Argonne, LLC and the U.S. Department of Energy and by NASA through grants NNH08AH761 and NNH08ZDA001N, and the Office of Vehicle Technologies of the U.S. Department of Energy under contract DE-AC02-06CH11357. The electron microscopy was accomplished at the Electron Microscopy Center for Materials Research at Argonne National Laboratory, a U.S. Department of Energy Office of Science laboratory, operated under Contract DE-AC02-06CH11357 by UChicago Argonne, LLC.

1. Hardware Alignment for General WLI Scan
To obtain quantitative information through WLI, the following steps may serve as a guideline. It is assumed that the operator has basic knowledge of interferometer operation. The guidelines are common regardless of the specific instrument. For some investigations, the specimen will be flat. For others, the specimen may be curved.
<ol>
	<li>Place the sample on the stage with the feature (ion sputtered crater, ion beam/ablated spot, or wear scar) facing straight up. Use a low-magnification objective and focus the instrument on it. For best resolution obtain an image in which the object of interest largely fills the screen, see Figure 2 for an example of a ball.</li>
	<li>Adjust the vertical position of the specimen so that interference fringes appear near the feature of interest. For a flat surface it is desirable that the specimen is tilted such that the plane is perpendicular to the optical axis, i.e. the fringe spacing will be large. For a curved surface (e.g. a ball), the specimen should be oriented such that fringes are centrally located around the feature, such as in Figure 3.</li>
	<li>Obtain a scan according to the instrument instructions. It may be necessary to adjust the illumination or scan height in order to obtain the best topographic map. Fill in any bad or missing data using the interpolate function, and then save the topographic map.</li>
</ol>
2. Volume Analysis Using Generic Software
In tribology, testing machines often employ non-conformal contact testing geometries such as a ball or a cylinder that is slid or rotated against a flat or another cylinder. Typically, material is lost at the point of sliding contact, although sometimes material may transfer from one surface to another, and this "transfer layer" will be measured as a surplus of material on one of the contacting specimens. Because the wear scar is three-dimensional and irregular in nature, optical profilometry may be the only technique suitable for obtaining accurate wear volume measurements - approximations are not valid. The goal is to measure the very small amounts of material which may be lost (or gained) in the contacting region at the completion of a test.
The basic principle of measurement is to define a mathematical plane at the level of the undisturbed surface: surface analysis software assumes that there is a "solid surface" (zero level), whatever above this level is "empty." The analysis function that measures the integrated removed volume below the plane of the "solid surface" will be referred to as "void volume." The function that measures the integrated volume above the plane of the "solid surface" (e.g. an accumulation of debris) will be called the "material volume."
Real undisturbed surfaces are seldom perfectly smooth and flat. For greatest accuracy in measuring small features it is good practice to define an area of interest (AOI); the area outside of which is excluded from analysis. The AOI is used to restrict the measurement area because irregularities in the surface contribute additional volume to the calculations that is not truly from the disturbed area.
 
3. Flat Surface - Mechanical Wear Analysis
<ol>
	<li>Volume analysis of a flat surface with a trench scar or depression, whether generated by mechanical wear, ion beam sputtering, or laser ablation, is easy to perform. Obtain an image such as Figure 4 left which shows a mechanical scar on a polished steel surface. Select an AOI that excludes the depression and then use whatever tilt and/or curvature removal function is available to level the undisturbed surface to maximum flatness. Then use the software to set the average surface height to Z=0. Figure 4 right is a pseudocolor view of a scar on a flat surface after these steps. In this view the excluded "void volume" is tinted red. In this color scheme, the dark brown denotes low areas, while orange denotes high areas.</li>
	<li>Delete the AOI. If the software has an automated volume measuring function, place a region of measurement over the scar. In this software, the measuring function will tally the "void and material volume" shown with blue tint in Figure 5. Total wear is "material volume" above the plane subtracted from "void volume." This is the volume change of the disturbed surface. (For software that does not have this function, but does have a histogram, or to clearly visualize which areas are raised above the surface or are below the surface, skip step 3.2 and go to step 3.3.)</li>
</ol>
The following three steps describe an alternate method of measuring wear volume.
<ol start="3">
	<li>Invert the AOI from step 3.1 to enable the scar region to be analyzed (the scar is included now).</li>
	<li>Generate a histogram of the data. The histogram is a graph of vertical height on the abscissa vs. the frequency of occurrence on the ordinate. Place one cursor at the Z=0 position (Figure 6 left). This may not be at the peak of the histogram. In this figure the cursors have been set up to selectively analyze only the missing material below the plane. The software integrates the total volume between the two cursors. The red tinted area shows what is omitted. The orange untinted areas in Figure 6 right are below the surface. The histogram function should generate a "void volume" number with the cursors positioned as shown to measure the material lost from the surface.</li>
	<li>Using the same histogram, place the other cursor this time at the Z=0 height position (Figure 7 left), and the other at the opposite end. The orange untinted areas in Figure 7 right are above the surface. The histogram function should generate a "material volume" number, i.e. surplus material raised above the flat surface. Total wear is "material volume" subtracted from "void volume," the same as in step 3.2. The histogram method should give the same wear volume as in step 3.2, but it provides additional details about the distribution of raised and lowered material, and shows a map of the distribution of this area.</li>
</ol>
In the example above there is no net material lost from the wear scar, instead there is material gain. This is unusual, but sometimes occurs when material transfers from one test counterface to another.
The same "flat surface characterization" approaches are beneficial for obtaining volumes removed in experiments with ion sputtering and laser ablation, considered in examples that follow.
4. Flat Surface - Craters and Ion Beam Profiles Measurements to Estimate Sputtering Yield, and to Perform Time-to-depth Calibration
As an alternative to the known and widely employed method for estimating sputtering yields using mass-loss method, based on direct weighing or quartz microcrystal balance,8, 9 we find that the WLI method is useful for direct visualization of the sputtered ion beam spots/craters obtained by static sputtering/raster scanning of an ion beam. Figure 8 compares longitudinal cross sections of a spot (green solid and blue dotted lines) of a normally incident static 5 keV and 150 eV Ar+ ion beams against their craters (olive open circles and cyan open diamonds) obtained by 100&times;100 pixels digital raster scanning of the same ion beam over the surface of a Cu(110) single crystal. The curve corresponding to the static beam overlaps one edge of the crater to demonstrate how raster scan of the ion beam generates the crater during sputter depth profiling.
5. Flat Surface - Characterization of Ultrafast Laser Ablation
Ultrafast laser ablation is recognized as a method for removing material from a solid while minimizing the heat affected zone.10 This process enables high rate micromachining with high aspect ratios and minimal damage (cracking, oxidation) to the remaining material, and opens up the possibility of efficient ablation of transparent materials.11 More recently, interest has developed in using ultrafast ablation as an analytical tool.12-15 The high nonlinearity of the ablation process also provides a means of reducing the ablated spot size significantly below the irradiated spot size (as typically defined by 1/e2) and even below the diffraction limit, as has been demonstrated.16 Depth resolution, while not competitive with the best ion beam methods, may be &lt;20 nm. Removal rates can easily be increased nonlinearly by increasing the laser fluence, so that very rapid profiling through microns of material is possible. Ideally, characterizing material removal by ultrafast ablation requires a technique that is fast and quantitative and well calibrated, all characteristics fulfilled by WLI.
Figure 9 shows pseudocolor images of two neighboring craters formed by repetitive ablation of GaAs with an ultrafast (60 fs, 800 nm) laser beam focused to a spot size of &asymp;8 &mu;m and having fluences corresponding to 0.4 and 1.0 J/cm2.
6. Curved Surfaces - Mechanical Wear Analysis
Volume analysis of a curved regular surface (ball or cylinder) is similar to that of a flat, but requires curvature removal. The following protocol shows an analysis of a circular wear scar on a steel ball. To find the volume lost from a ball it is necessary to do mathematical processing to transform a ball with a flat area into a flat plane with an indentation, then measure the volume of the indentation as was done in Section 3 on flat surfaces. A wear scar on a ball will be measured, first using the simpler automatic technique, then with the histogram technique.
<ol>
	<li>Figure 10 left shows an isometric view of a wear scar on a ball. Select an AOI that excludes the wear scar, and select the software curve fitting tool that will transform the surface so that it is a worn depression in the middle of an undisturbed flat area. Because curvature removal may be an iterative technique it may be necessary to run the fit several times so that the undisturbed area is flat to nm level accuracy. Any visible non-uniformity outside of the wear scar indicates a problem and the calculation will not be correct. Set the average height outside the scar to Z=0. Figure 10 right shows a pseudocolor view of the scar after curvature removal and setting Z=0 with an AOI properly masking the worn area.</li>
	<li>Use the measuring tool, if available, to analyze the wear, as shown in Figure 11. Total wear volume is "material volume" subtracted from the "void volume."</li>
</ol>
The following steps describe an alternate method of measuring wear volume.
<ol start="3">
	<li>In the same manner as step 3.3, invert the AOI so that the wear scar is included. Generate a histogram of the data. Place one cursor at the Z=0 position (Figure 12 left). The orange untinted areas in Figure 12 right are below the surface. The histogram function should generate a "void volume" number.</li>
	<li>Using the same histogram, place the other cursor this time at the Z=0 height position (Figure 13 left), and the other at the opposite end. The orange untinted areas in Figure 13 right are above the surface. The histogram function should generate a "material volume" number. Total wear volume is "material volume" above the plane subtracted from "void volume," the same as in step 3.2. The histogram method should calculate the same wear volume as in step 6.2, but it provides additional details about the distribution of raised and lowered material, and shows a map of the distribution of this area.</li>
</ol>

No conflicts of interest declared.

Example 1
WLI is not widely used for surface characterization in tribological work, but it is in fact a powerful method for quantitative measurement of wear volumes for many contact geometries. WLI produces a full 3D representation of the surface that can be analyzed using any of several visualization software packages. These packages enable various types of measurements to be performed. For greater lateral resolution, images can be "stitched" together to produce wide-area information (several mm...

The surface of solid materials determines to a large extent properties of interest for those materials: electronically, structurally, and chemically. In many areas of research, the addition of material (for instance, thin film deposition by pulsed laser/magnetron sputtering deposition, physical/chemical vapor deposition), removal of material (reactive ion etching, ion sputtering, laser ablation, etc.), or some other processes, need to be characterized. Additionally, surface modification through interaction with energetic light pulses or charged particles has numerous applications and is of fundamental interest. Tribology, the study of friction and wear, is another area of interest. On a benchtop scale, a multitude of tribological test geometries exist. Non-conformal contact geometries may be used, and a ball or cylinder may be slid or rotated against a flat surface, another ball, or cylinder, for a length of time, and the amount of material that is removed is measured. Because the wear scar is three-dimensional and irregular in nature, optical profilometry may be the only technique suitable for obtaining accurate wear volume measurements. Common analysis tasks include also surface roughness parameters, step height, loss of material volume, trench depth, and so on; all of them can be obtained additionally to simple 2D and 3D topography visualization.
Optical profilometry refers to any optical method that is used to reconstruct the profile of surfaces. Profilometric methods include white light interferometric, laser, or confocal methods. Some optical profilometers obtain information through approaches based on conventional diffraction-limited microscope objectives. For example, a scanning laser may be integrated with a microscope to obtain topographic and true color information of surfaces. A second method uses a technique which exploits the extremely small depth of focus of conventional objectives to assemble a series of in-focus "image slices" of the surface to obtain a 3D topographic map.
In this work we show how a white light interferometric microscope/profilometer enables the measurement of the amount of material lost during mechanical wear processes, or during material etching processes such as ion sputtering craters or laser ablation. Most attention is paid to methodology of this method to illustrate its large installed capacity that makes it widely available and attractive for numerous applications. Most types of WLI employ the Mirau technique, which uses a mirror internal to the microscope objective to cause interference between a reference light signal and the light reflected from the sample surface. The choice of Mirau interferometry is dictated by simple convenience, because the entire Mirau interferometer can be fit inside the microscope objective lens and coupled to a regular optical microscope (Figure 1). A series of two-dimensional interferograms are acquired with a video camera, and software assembles a 3D topographic map. The white light source supplies broad spectrum illumination which helps to overcome the "fringe order" ambiguity inherent to a monochromatic source. A monochromatic source of light may be used to obtain more accurate measurement of shallow topographic features. The lateral resolution is fundamentally limited to &lambda;/2 (numerical aperture, NA=1), but in most instances is larger, being determined by the NA of the objective, which is in turn connected to magnification/field-of-view size. Table 1 in Ref. 1 has a direct comparison of all mentioned parameters. Depth resolution approaches &asymp;1 nm, being a function of the interferometric nature of the technique. Further information on Mirau WLI can be found in Refs. 2, 3. An introduction on white light interferometric approach can be found in Ref. 4.
Other methods for analysis of surfaces are atomic force microscopy (AFM), scanning electron microscopy (SEM), and stylus profilometry. The WLI technique compares favorably to these methods and has its own advantages and drawbacks that are due to the optical nature of the method.
The AFM is capable of obtaining 3D images and thus corresponding cross sections, but AFM has a limited scanning ability in the lateral (&lt;100 &mu;m) and depth (&lt;10 &mu;m) axes. In contrast to those, the main advantage of WLI is the flexible field-of-view (FOV) of up to a few millimeters with simultaneous real 3D imaging capability. In addition, as we will demonstrate it has wide vertical scanning range capacity, allowing one to solve a variety of problems of surface modification simply. Researchers who have worked with AFM are aware of the problem with plane positioning of a sample when measuring prolonged features of low vertical gradients. Generally, one may think of WLI/OP as an "express" technique over AFM. Of course, there are a number of areas for which only AFM is suitable: when lateral features to be resolved have characteristic dimensions smaller than the lateral resolution of WLI, or instances where data from WLI is ambiguous due to unknown or complex optical properties of a sample in a way that affects the accuracy of measurements (to be discussed later), etc.
The SEM is a powerful way to look at surfaces, being very flexible in terms of the FOV size with large depth of focus, larger than any conventional optical microscope can offer. At the same time, 3D imaging by SEM is cumbersome, particularly as it requires taking of stereo-pair images that then are converted to 3D images by the anaglyphic method, or through observing with optical viewers, or used for direct calculation of depths between different points of interest on a sample.5 By contrast, WLI/OP profilometry offers easy-to-use 3D reconstruction with simultaneously flexible FOV. WLI scans through the full height range needed for the particular sample (from nanometers to hundreds of microns). WLI is unaffected by the electrical conductivity of the sample material, which may be a problem with SEM. WLI clearly does not require a vacuum. On the other hand there are a number of applications for which SEM provides superior information: lateral features to be resolved of characteristic dimensions below the lateral resolution of WLI, or cases where different parts of a sample can be topographically distinguished only when secondary electron emission coefficients differ.
One more technique for surface inspection, which is widely used in secondary ion mass spectrometry6 and in the field of microelectromechanical systems characterization7 is stylus profilometry. This technique is popular because of its simplicity and robustness. It is based on direct mechanical contact scanning of a stylus tip over the sample surface. This is a coarse contact tool, which is able to scan along a single line at a time. It makes 3D surface raster-scan imaging extremely time consuming. Another drawback of the stylus technique is the difficulty of measuring surface features of high aspect ratio and of size comparable with its characteristic tip size (submicron to several microns typically) that implies a tip radius and a tip apex angle. An advantage of stylus profilometry is its insensitivity to varying optical properties of a sample, which can affect the accuracy of WLI/OP measurements (to be discussed later).
The surface maps in the present article were obtained using a conventional Mirau-type WLI (Figure 1). Many companies such as Zygo, KLA-Tencor, nanoScience, Zemetrics, Nanovea, FRT, Keyence, Bruker, and Taylor Hobson produce commercial table-top OP instruments. The acquired maps were reconstructed and processed using commercial software of the type that is commonly used for WLI, scanning electron, or probe microscopy. The software has the ability to perform mathematical manipulations of the surface, cross section profile analysis, void and material volume calculations, and plane correction. Other software packages may automate some of these features.

<table border="1">
 <tbody>
 <tr>
 <td>Single crystal substrates of Si, GaAs and Cu </td>
 <td></td>
 <td></td>
 <td>for sputtering and ablation </td>
 </tr>
 <tr>
 <td>Pure metal alloys </td>
 <td></td>
 <td></td>
 <td>for tribology examples</td>
 </tr>
 </tbody>
</table>

characterization of surface modifications by white light interferometry: applications in ion sputtering, laser ablation, and tribology experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

<img alt="Figure 1" src="/files/ftp_upload/50260/50260fig1.jpg" /> 
 Figure 1. Photograph of a simple profilometer used in the present study: a multiple objective turret is seen in the picture. Two objectives are standard (10x and 50x), and two are Mirau objectives (10x and 50x). This microscope has an intermediate magnification feature that enables step-wise magnification multipliers of 0.62, 1.00, 1.25, or 2.00 to be selected. <a href="https://www.jove.com/fi...

Watch this Scientific Journal Video about Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments at JoVE.com

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

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15.5K Views.  Argonne National Laboratory. White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

Video: Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

Fabrication And Characterization Of Photonic Crystal Slow Light Waveguides And Cavities

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view and for its considerable potential for practical applications. Slow light photonic crystal waveguides, in particular, have played a major part and have been successfully employed for delaying optical signals1-4 and the enhancement of both linear5-7 and nonlinear devices.8-11
Photonic crystal cavities achieve similar effects to that of slow light waveguides, but over a reduced band-width. These cavities offer high Q-factor/volume ratio, for the realization of optically12 and electrically13 pumped ultra-low threshold lasers and the enhancement of nonlinear effects.14-16 Furthermore, passive filters17 and modulators18-19 have been demonstrated, exhibiting ultra-narrow line-width, high free-spectral range and record values of low energy consumption.
To attain these exciting results, a robust repeatable fabrication protocol must be developed. In this paper we take an in-depth look at our fabrication protocol which employs electron-beam lithography for the definition of photonic crystal patterns and uses wet and dry etching techniques. Our optimised fabrication recipe results in photonic crystals that do not suffer from vertical asymmetry and exhibit very good edge-wall roughness. We discuss the results of varying the etching parameters and the detrimental effects that they can have on a device, leading to a diagnostic route that can be taken to identify and eliminate similar issues.
The key to evaluating slow light waveguides is the passive characterization of transmission and group index spectra. Various methods have been reported, most notably resolving the Fabry-Perot fringes of the transmission spectrum20-21 and interferometric techniques.22-25 Here, we describe a direct, broadband measurement technique combining spectral interferometry with Fourier transform analysis.26 Our method stands out for its simplicity and power, as we can characterise a bare photonic crystal with access waveguides, without need for on-chip interference components, and the setup only consists of a Mach-Zehnder interferometer, with no need for moving parts and delay scans.
When characterising photonic crystal cavities, techniques involving internal sources21 or external waveguides directly coupled to the cavity27 impact on the performance of the cavity itself, thereby distorting the measurement. Here, we describe a novel and non-intrusive technique that makes use of a cross-polarised probe beam and is known as resonant scattering (RS), where the probe is coupled out-of plane into the cavity through an objective. The technique was first demonstrated by McCutcheon et al.28 and further developed by Galli et al.29

Use of photonic crystal slow light waveguides and cavities has been widely adopted by the photonics community in many differing applications. Therefore fabrication and characterization of these devices are of great interest. This paper outlines our fabrication technique and two optical characterization methods, namely: interferometric (waveguides) and resonant scattering (cavities).

Slow light has been one of the hot topics in the photonics community in the past decade, generating great interest both from a fundamental point of view ...

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active layer which consists of blue-fluorescent poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and &#960;-conjugated triphenylamine molecules. This white light emission originates from exciplexes formed between PFD and amines in electronically excited states. A device containing PFD, 4,4&#39;,4&#39;&#39;-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), Poly(ethylene oxide) and K2CF3SO3 showed white light emission with Commission internationale de l&#39;&#233;clairage (CIE) coordinates of (0.33, 0.43) and a Color Rendering Index (CRI) of Ra = 73 at an applied voltage of 3.5 V. Constant voltage measurements showed that the CIE coordinates of (0.27, 0.37), Ra of 67, and the emission color observed immediately after application of a voltage of 5 V were nearly unchanged and stable after 300 sec.

The authors present a method for fabricating stable white-light-emitting electrochemical cells utilizing emission from exciplexes formed between a blue-emitting fluorene polymer and aromatic amines.

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 &#181;m-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

This paper presents a microfabrication methodology for surface ion traps, as well as a detailed experimental procedure for trapping ytterbium ions in a room-temperature environment.

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due ...

Production and Characterization of Vacuum Deposited Organic Light Emitting Diodes

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex donor-acceptor emitters is presented. With a step-by-step procedure, readers will be able to repeat and produce OLED devices based on simple organic emitters. A patterning procedure allowing the creation of personalized indium tin oxide (ITO) shape is shown. This is followed by the evaporation of all layers, encapsulation and characterization of each individual device. The end goal is to present a procedure that will give the opportunity to repeat the information presented in cited publication but also using different compounds and structures in order to prepare efficient OLEDs.

A protocol for the production of simple structured organic light-emitting diodes (OLEDs) is presented.

A method for producing simple and efficient thermally-activated delayed fluorescence organic light-emitting diodes (OLEDs) based on guest-host or exciplex ...

Shaping the Amplitude and Phase of Laser Beams by Using a Phase-only Spatial Light Modulator

The aim of this article is to visually demonstrate the utilization of an interferometric method for encoding complex fields associated with coherent laser radiation. The method is based on the coherent sum of two uniform waves, previously encoded into a phase-only spatial light modulator (SLM) by spatial multiplexing of their phases. Here, the interference process is carried out by spatial filtering of light frequencies at the Fourier plane of certain imaging system. The correct implementation of this method allows arbitrary phase and amplitude information to be retrieved at the output of the optical system.
It is an on-axis, rather than off-axis encoding technique, with a direct processing algorithm (not an iterative loop), and free from coherent noise (speckle). The complex field can be exactly retrieved at the output of the optical system, except for some loss of resolution due to the frequency filtering process. The main limitation of the method might come from the inability to operate at frequency rates higher than the refresh rate of the SLM. Applications include, but are not limited to, linear and non-linear microscopy, beam shaping, or laser micro-processing of material surfaces.

We show how to encode the complex field of laser beams by using a single phase element. A common-path interferometer is employed to mix the phase information displayed into a phase-only spatial light modulator to finally retrieve the desired complex field pattern at the output of an optical imaging system.

The aim of this article is to visually demonstrate the utilization of an interferometric method for encoding complex fields associated with coherent laser ...