Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

The overall goal of this experimental procedure is to grow single crystalline bismuth nanowires in a scalable manner through thermal evaporation in a high vacuum. This method can be used to synthesize high quality business nanos in high yields. The material has been of great interest in the field of semi electricity studies.

The main advantage of this technique is that it involves no catalysts or seeds, and that the synthetic procedure is taken place in high vacuum so that the nano wire is being formed as of hyper purity. This method provides insight into how nanoscale porosity induces spontaneous business nano wire growth, but it should be also be applicable to other systems with a low melting point, such as Indio and tin. To begin vent the deposition chamber to atmospheric pressure and open the chamber.

The venting is done by pressing the start PC venting button on the control software interface, which automatically starts a sequence that vents the chamber to atmospheric pressure. On reaching the atmospheric pressure. Open the chamber by pulling the front accessing door.

Then mount a tungsten evaporation boat between a pair of thermal evaporation electrodes. Place one gram of bismuth pellets into the evaporation boat mount a vanadium sputtering target to the magnetron sputtering source. Next, connect the mini banana connectors of the closed loop temperature controller to the electrical feed through of the deposition system.

To clean the growth substrates by oxygen plasma, place the growth substrates into a plasma cleaner and pump the chamber by pressing on the vac on button to its base pressure of 10 millitorr. Open the oxygen gas valve and introduce oxygen gas to the chamber by pressing the gas on button on the front panel. Adjust the flow rate by pressing the INCR and DECR buttons for gas flow rate control to maintain a chamber pressure of about 100 millitorr.

Next, set the plasma power at 20 watts by pressing the INCR and DECR buttons for power control and ignite the plasma by pressing the RF on button. Wait for five minutes before turning off the plasma by pressing the RF on button. Then vent the chamber by pressing the bleed button before retrieving the substrates to load substrate.

First, mount the substrate temperature control assembly to the substrate holder. Use spring clips to mount the growth substrates on top of the peltier cooler heater assembly. Then mount the fully assembled substrate holder into the vapor deposition chamber.

With the substrates facing the deposition sources, connect the electrical feed throughs to the peltier cooler heater assembly. Close the substrate shutter to avoid unintentional deposition to the substrate. Next, start pumping down the deposition chamber.

The pumping is done by pressing the start PC pumping button on the control software interface, which automatically starts a sequence that pumps the chamber to its base pressure to deposit vanadium with a magnetron sputtering source Start argon flow in the sputtering source. Set the flow rate to between 40 and 50 standard cubic centimeters per minute. Adjust the turbomolecular pumps revolution rate for a chamber pressure of 2.5 to three millitorr while the chamber is gradually reaching its steady state pressure.

Set the thickness calibration factors to the quartz crystal micro balance or QCM for vanadium. The density is 5.96 grams per cubic centimeter, and the Z factor is 0.530. Turn on the DC sputtering source and set the power at 200 to 250 watts without opening the substrate shutter.

Keep the source running for two minutes. Open the substrate shutter to start vanadium deposition. In the meantime, reset the accumulated thickness of the QCM to zero.

Continue deposition until an apparent thickness of 20 nanometers is accumulated per QCM reading. Then close the substrate shutter, gradually decrease the sputter power to zero. Then turn the source off, shut off the argon flow.

Finally return the turbomolecular pump to its full power. It's very important that the substrate temperature are maintained stably and precisely as this, and the lines of the nano virus are strongly tailored by the temperature For bismuth deposition at temperatures above or below room temperature, set the desired value to the temperature controller. Wait until the desired temperature is reached.

Set the thickness calibration factors to the QCM for bismuth. The density is 9.78 grams per cubic centimeter, and the Z factor is 0.790. Turn on the thermal evaporation power supply to the bismuth source.

Then slowly increase heating power to the tungsten boat until the deposition rate of two angstroms per second is achieved. Per QCM reading, reset the accumulated thickness of the QCM to zero. In the meantime, open the substrate shutter to start bismuth deposition.

Continue deposition until an apparent thickness of 50 nanometers is accumulated. Then close the substrate shutter. Gradually decrease the thermal evaporation power to zero.

Turn the source off. Turn off the power supply to the thermal electric cooler heater. Vent the deposition chamber to atmospheric pressure and open the chamber.

Finally, retrieve the substrate holder and collect the bismuth nano wire covered substrates. The cross-sectional scanning electron microscopy or SEM images of vanadium underlay formed by magnetron, sputtering and thermal evaporation methods are presented here.Here. SEM images are presented for bismuth nanowires formed at different substrate temperatures.

The crystal structure of the bismuth nanowires is determined through transmission electron microscopy, selective area electron diffraction, and x-ray diffraction studies. Elemental analysis by energy dispersive x-ray spectroscopy indicates that the bismuth nanowires are not alloyed with the vanadium underlayer. After watching this video, you should have a good understanding of how to sly grow.

Single crystalline business nano wears through thermal evaporation in the high vacuum While attempting this procedure, it is important to control the substrate temperature precisely as it can significantly affect the dimension of the nano wears. Low base pressure is also critical to avoid the oxidation of devastated materials after its development. This technique paved the way for the searchers in the field of phy synthesis of nanostructures to utilize surface energy as a driven force for high quality and hyper nanostructures.