Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

The overall goal of this procedure is to use the focused ion beam technique in order to observe omic contact fabrication on the individual nano structures of layers, semiconductor materials. This method can help answer key questions in the nanotechnology fields, such as how to make good omic contact on individual nano materials without alne treatment. The main advantage of this technique is that the fo iron beam metal Deion approach provides highly reproducible electric contest on individual layer semiconductor nanostructures.

The whole process is also relatively simple in comparison to other techniques such as trobin discography After structural characterization of the molybdenum di selenide layer crystals as described in the accompanying text protocol. Begin fabrication of the molybdenum di selenide layer Nano Krystal devices. First, clean a pair of tweezers with acetone and then alcohol.

Use the tweezers to pick out four to eight pieces of the molybdenum di selenide layer crystals with a shiny surface and an area larger than 0.5 millimeters by 0.5 millimeters. Put each crystal on a piece of dicing tape with an area of 20 millimeters by 60 millimeters. Fold the tape in half to exfoliate the layer.

Crystal, repeat this action approximately 20 times. Usually layer crystals can be stripped into numerous micrometer sized crystals. Obtain three silicon dioxide coated silicon substrates with 16 pre-PA titanium gold electrodes on the surface.

The area of each template should be approximately five millimeters by five millimeters square. Place the dicing tape with the layer nano Krystal powder upside down on each device template. Tap the dicing tape lightly so that approximately 10 to 100 pieces of the maum diselenide layer crystals fall onto each template.

Mount the prepared templates on a focused ion beam holder using conducting copper foil tape. Then load the holder into the focused ion beam chamber. Evacuate the chamber to one times 10 to the fifth millibars by clicking on pump.

For the SEM mode, set the electron beam current to 41 pico amps and the acceleration voltage to 10 kilovolts. Next, for the FIB mode, set the ion beam current to 0.1 nano amps and the acceleration voltage to 30 kilovolts. Then warm up the ion beam system and the gas injection system.

Turn on the electron beam by clicking the button beam on and focus the image at a low magnification of 100 x. Next, set the Z axial working distance to 10 millimeters for SEM mode. Now increase the magnification to 5, 000 x and focus on the sample.

Once focused, input a tilt angle of 52 degrees into the navigation menu to tilt the angle of the holder. Next, select rectangular and square shaped molybdenum di selenide. Layer nano crystals with a thickness ranging from five to 3000 nanometers.

For electrode fabrication, take SCM images of the targeted pristine material at different magnifications ranging from 1000 x to 10, 000 x before electrode fabrication. Next, switch to focused ion beam mode and take an image using snapshot mode to reduce the exposure time of the targeted material under ion beam bombardment. Define the electrode deposition area by first selecting the platinum deposition mode, and then input the thickness as 0.2 to 1.0 micron.

Next, introduce the capillary of the gas injection system into the chamber by clicking on the platinum deposition box in the gas injection block. Take another image using the snapshot mode and modify the position of the electrodes. If the originally defined pattern shifts slightly, then turn on the focused ion beam deposition After deposition, draw the capillary of the gas injection system back by unclicking the platinum deposition box.

Next, switch to the scanning electron microscope mode and take images at different magnifications of the completed devices with two or four electrodes. After taking the images, set the tilt angle of the holder, return to zero degrees and take additional top view images at different magnifications in order to estimate the material width and electrode inter distance. When finished, turn off the electron beam and ion beam systems and cool down the gas injection system.

Also, vent the chamber with nitrogen gas and then take the holder out of the chamber. Finally, close the chamber door and evacuate the chamber. One last time.

Representative field scanning electron microscope images of the two terminal and four terminal molybdenum IDE devices are shown here. After using a FM to estimate the height of a number of nano flakes, the omic contacts of the devices can be characterized by measuring the current versus voltage relationship. The current voltage curves of this device follow a linear relationship confirming the omic contact condition of the molybdenum di selenide devices.

A cross-sectional transmission electron microscopy image of the platinum molybdenum di Selenide interface shows that an alloy layer of about 25 to 30 nanometers was formed between the platinum and molybdenum di selenide because of ion beam bombardment. A high resolution TEM image of the interface shows that an amorphous alloy is formed at the surface of the single crystal molybdenum di selenide. This alloy consists of a mixture of molybdenum, selenium, and platinum at a ratio of two to four to one Once mastered.

This technique can be done in hours if it is performed properly after its development. This technique path the way for researchers in the field of nanotechnology and material science, so explore electric properties in their semiconductor material systems.