Name: fabrication of spatially confined complex oxides
Uploaded: 2013-07-01T13:00:00
Description: Watch this Scientific Journal Video about Fabrication of Spatially Confined Complex Oxides at JoVE.com

This effort was wholly supported by the US DOE, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.

1. Sample Growth Fabrication
<ol>
 <li>Clean a 5 mm x 5 mm x 0.5 mm single crystal substrate having a miscut angle &lt;0.1 degree such as SrTiO3 or LaAlO3 with acetone and then water in an ultrasonic cleaner for 10 min each. To get a TiO2 termination on SrTiO3, etch the substrate in 10% hydrogen fluoride for 30 sec and rinse in water for 1 min, followed by an anneal at 1,100 &deg;C for 10 hr. After cleaning, mount the substrate on a heater suitable for ultra-high vacuum condi...

<ol>
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X., Zhang, Z., Wu, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dependence+of+negative+differential+resistance+on+electronic+phase+separation+in+unpatterned+manganite+films.">Dependence of negative differential resistance on electronic phase separation in unpatterned manganite films.</a> Applied Physics Letters. 100, 62402-62404 (2012).</li><li>Ichimiya, A., I, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Reflection High Energy Electron Diffraction. , (2004).</li><li>Guo, H., Sun, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+diagram+of+La0.7Sr0.3MnO3+thin+films+using+pulsed+laser+deposition.">Growth diagram of La0.7Sr0.3MnO3 thin films using pulsed laser deposition.</a> arXiv. , 1210.5989 (2012).</li><li>Ward, T. Z., Gai, Z., Guo, H. W., Yin, L. F., Shen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+a+first-order+electronic+phase+transition+in+manganites.">Dynamics of a first-order electronic phase transition in manganites.</a> Physical Review B. 83, 125125 (2011).</li><li>Ward, T. 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Unlike single element semiconducting materials such as Si, the fabrication of complex materials can be more difficult due to the fact that the complex structure and multiple elements must all be taken into consideration. The use of photolithography to fabricate complex oxide devices is relatively low cost and fast to prototype as opposed to other confinement techniques. There are however some important limitations to understand. Photolithography has a spatial limitation to creating structures of about 1 micron so is not ...

The first and one of the most important steps towards high quality devices is the growth of epitaxial oxide thin films. A single crystal substrate is used as a "template" to deposit the target materials. Among different deposition methods, pulsed laser deposition (PLD) is one of the best ways to acquire good quality thin films 4,5. The growth processes involve heating the substrate to around 800 &deg;C in an oxygen environment and using laser pulses to hit the target material and generate a flux to be deposited onto the substrate. The typical system is shown in Figure 1.
While unpatterned films have been shown to reveal exotic new physics 6, reducing film dimension provides more opportunities to explore new phenomena and device fabrication. Photolithography can be used to shrink the in-plane sample dimension down to the order of 1 &mu;m. The detailed protocol of the photolithography process will be discussed below. This technique is compatible with most widely used substrates which allows for investigations of confinement effects on epitaxial films held at different strain states.
Since many complex oxides have interesting characteristics at low temperatures and/or high magnetic fields, the electronic connection between the device and measurement equipment is very important. High quality contacts can be formed by evaporating Au contact pads in a 4-probe geometry and with the use of a wire bonder to make connections between the pads and measurement device. When done correctly, these connections can easily withstand extreme measurement environments within wide temperature ranges of 4 K to 400 K and magnetic field ranges of up to &plusmn; 9 T.

<table border="1">
 <tbody>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Reagent/Material</td>
 </tr>
 <tr>
 <td>SrTiO3(001) &amp; LaAlO3(100) substrates</td>
 <td>CrysTec GmbH</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Microposit S1813 Photoresist</td>
 <td>Shipley</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>CD-26 Developer</td>
 <td>Shipley</td>
 <td>38490</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>GE varnish</td>
 <td>Lakeshore</td>
 <td>VGE-7031</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>&nbsp;</td>
 <td>Equipment</td>
 </tr>
 <tr>
 <td>Reflected High Energy Electron Diffraction (RHEED)</td>
 <td>Staib Instruments</td>
 <td>&nbsp;</td>
 <td>35 kV TorrRHEED</td>
 </tr>
 <tr>
 <td>Mask Aligner</td>
 <td>ABM</td>
 <td>Model 85-3 (350 W) Lightsource</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Resistivity Puck</td>
 <td>Quantum Design</td>
 <td>P102</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Wire Bonder</td>
 <td>Kulicke &amp; Soffa</td>
 <td>04524-0XDA-000-00</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

fabrication of spatially confined complex oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

This paper focuses mostly on the photolithography and wire-bonding aspects of sample preparation. More details on film growth procedures can be found in our other recent publications 8.
Photolithography is an important method to control dimensionality in complex oxides for the purpose of investigating electron correlation lengths and electronic phase separation 9-13. Figure 2 shows optical images of partial steps during the process. It is necessary to poi...

Watch this Scientific Journal Video about Fabrication of Spatially Confined Complex Oxides at JoVE.com

Fabrication of Spatially Confined Complex Oxides

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

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