Probing C₈₄-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

The aim of this study is the fabrication of a C84-embedded silicon substrate heterojunction and subsequent analysis to obtain a comprehensive understanding of the electronic, optoelectronic, mechanical, magnetic, and field emission properties of the resulting materials. Nanomaterials I have in forcator are a ranging trend of a material revolution. With the help of a skinny probe microscope we will be able to identify the characteristics of nanostructures on the surfaces with a sufficient and a resolution.

Using molecular dynamic simulation we can monitor the type, dependent, atomic, and mechanical behavior of the indentation process. All the simulating were preformed with parallel computing in a supercluster ALPS of NCHC and all the experiment work was done in the nanoscience lab of NCHU. The person who demonstrated the procedures will be Che-Fu, Pei-Fang, Ya-Chi, and Wei-Pin from my group.

First, subject a silicon 111 substrate to cleaning involving the application of a solvent followed by heating in an ultrahigh vacuum system for the removal of the oxide layer and impurities from the surface of the substrate. For C84 deposition on the silicon surface preheat a Castle evaporator with an external power supply through heating filaments to 500 degrees celsius to promote the out-gassing of impurities. Next, load C84 nanoparticles into a Castle container.

Then, resistively heat the Castle to 650 degrees celsius to vaporize the C84 nanoparticles. Now, evaporate the C84 nanoparticles in straight lines until they strike the silicon substrate through a controlled valve at a pressure below five times 10 to the minus eight pascal. Following this, pre in the ALBA silicon 111 substarate in an ultrahigh vacuum system at 900 degrees celsius to obtain the one by one structures.

Reduce the temperature to 650 degrees celsius for 30 minutes for the deposition of the C84 nanoparticles on the surface of the substrate. In the ALBA silicon substrate at approximately 750 degrees celsius for 12 hours during which time the powdered C84 nanoparticles self assemble into a highly uniform fullerene ray on the surface of the silicon 111 substrate. At this point, place the C84-embedded silicon substrate on a scanning probe microscopy, or SPM, sample holder.

Transfer the sample from the exchange chamber to a sample preparation chamber. Introduce the holder into a UHV-STM scanning head system and transfer the sample to an observation chamber. Then, sweep the applied sample bias from minus five to five volts.

Next, click on the IV measurement item to measure the tunneling current eye at atomic resolution. Choose at least 20 particular locations on the C84-embedded silicon substrate for the measurements. To measure the band gap energy obtain IV curves as previously described from the surfaces indicated in the text protocol.

Following this, place the C84-embedded silicon substrate on a field emission, or FE, sample holder. Insert the holder into the FE analysis chamber. Then, evacuate the chamber to a pressure of approximately five times 10 to the minus 5 pascal for the FE measurement.

Increase the applied voltage manually on the substrate from 100 to 1, 100 volts. Measure the corresponding field emission current as a function of applied voltage using a high voltage source measurement unit with a current amplifier. Now, place the testing substrate in the center of the sample compartment of an optical emission measurement system.

Then, focus a helium cadmium laser source with 325 nanometer emissions. After setting up the spectrometer acquire the photoluminescence spectrum by collecting and analyzing the emitting photons. Magnetize samples of the C84-embedded silicon substrate prior to magnetic force spectroscopy, or MFM measurements, by applying a magnet with a field strength of approximately 2 kilo oersted.

After placing the magnetized sample on the MFM sample stage observe the microstructure of the fullerene in the magnetic domain embedded within the silicon substrate using MFM in lift mode with the application of magnetization perpendicular to the surface of the sample. Following this, magnetize samples of the C84-embedded silicon substrate and C84 clusters on the C84-embedded silicon substrate prior to SQUID experiments by applying a magnet with a field strength of approximately 2 kilo oersted. Place the magnetized sample in the SQUID.

Then, apply a sweeping magnetic field in a range of approximately 2 kilo oersted. Obtain the magnetization loops plotted versus the external magnetic field in SQUID measurements at room temperature. To measure the stiffness of the C84-embedded silicon substrate, first place one of the substrates on an AFM, or atomic microscope, sample stage.

Next, obtain force measurements under atmospheric conditions from the appropriate silicon substrates. Obtain force measurements as previously described using the AFM and a UHV system from the appropriate silicon substrates. To prepare the silicon substrate, turn on the OSSD software.

Click of the search button to show the search criteria panel. Choose silicon substrate, elemental type, reconstructed structure, semi-conductor elec, diamond lattice, 111 face, and seven by seven pattern. Then click on the search and accept buttons to display the structure list panel.

Click the desired structure silicon 111 seven by seven surface. Now, click the file button and save the coordination file as a xyz file. Next, turn on the Ovito software, load the xyz file into the software, and use the slice command to capture a super cell of the silicon 111 seven by seven surface structure with the appropriate size, 26.878 by 46.554 angstrom squared in the X and Y directions.

Use the simulation cell command to adjust the cell size in the X and Y directions and shift the cell to the origin point of zero. Use affine transformation and click transform matrix to shift the model 5.714 angstroms in the normal direction. Use the slice command to cut the bottom most atom layer in the normal direction.

Export the data file with the format of LAMMPS. With LAMMPS data file format, the cell boundary will be defined. Reload the data with the format of LAMMPS into the Ovito.

Use the wrap at periodic boundaries command to rearrange the structure inside the cell. Use affine transformation and click transform matrix to shift the model 84.6 angstroms in the normal direction. Use the simulation cell command to adjust the cell size 150 angstroms in the Z direction.

Export the data file with the format of LAMMPS. Reload the data into the Ovito. Use show periodic images to duplicate a five by three super cell in the X and Y directions to enlarge the size of the substrate.

Export the data file with the format of LAMMPS. After preparing a coordination file of the silicon 111 super cell with the appropriate size load the data into Ovito. Use show periodic images to duplicate a five by three by eight super cell in the X, Y, and Z directions to enlarge the size of the substrate.

Use affine transformation and select transform matrix to shift the model to the origin point in the Z direction 37.6184 angstroms. Export the data file with the format of LAMMPS. Combine the data files of the silicon 111 seven by seven surface and the silicon 111 substrate models using a text editor.

The silicon 111 seven by seven substrate model is ready. To prepare the C84 fullerene mono-layer, download the coordination file of the C84 fullerene from the web. Use a homemade program to duplicate seven by seven C84 fullerenes arranged in a honeycomb structure.

Next, use a homemade program to lay the C84 mono-layer on the silicon 111 seven by seven surface with the distance of three angstroms. Use the load data command to load the simulation model in LAMMPS script. Then, set up the region and create atom commands to create a five nanometer spherical probe.

Finally, prepare an input script of LAMMPS for indentation simulation and calculate the detail mechanical properties. A mono-layer of C84 molecules on a disordered silicon 111 surface was fabricated using a controlled self assembly process and a series of topographic images measured by UHV-STM with various degrees of coverage are shown here. The electronic and optical properties of the C84-embedded silicon substrate were investigated using STM and photoluminescence analysis techniques.

The excellent material properties of the samples demonstrate how nanotechnology can be used for the control of matter at the atomic and nano scales. The MFM and SQUID results show the surface magnetism of C84-embedded substrate. The UHV-AFM results demonstrate the potential of the C84-embedded silicon substrate as an alternative to semiconductor carbide in nanoelectronic devices for high temperature, high power, high frequency applications.

As well as in magnetic and microelectromechanical systems. The molecular dynamic simulation process on the nanoindentation of C84-embedded substrate is shown here. The mechanical properties of the fullerene embedded substrate are shown here.

The corresponding snapshots as a function of indentation depth can be seen here. The results of indentation force as a function of indentation depth are used to calculate the hardness, reduced modulus, and bloating stiffness of the C84 mono-layer. It's now a popular perception that a nanomaterial will bring up a applicable development in science and technologies because of layer unit of chemical, physical, and the mechanical properties.

With only one mono-layer of fullerene the properties of the silicon substrate can be changed dramatically. In our study, fullerene embedded silicon substrate has a waving edge, good fuel emission properties, and a high strength, and also is the fullerene magnetic. I believe our proposed substrates will have a better performance in a wider application in nanotechnology.

After watching this video you should have a good understanding of how to perform experiments and simulations for surface magnetism. The demonstration of these comprehensive techniques will pave the way for researchers to explore the fundamental properties of materials.