Motivation Cd 3 As 2, being a Dirac-type semimetal (DTS), is of considerable research interest due to its high electron mobility, and being a 3D analogue of graphene whose electron mobility is much higher than that of silicon Due to its three dimensional structure, Cd 3 As 2 could be used for constructing electronic devices rather than just performing as a laboratory for electrons in a DTS Objectives Understand interdependent relationships between elemental concentrations, temperature gradients, total and partial pressures, mass transport, and diffusion Determine and optimize the general parameters that are required to produce crystalline platelets of cadmium arsenide by the process of chemical vapor deposition Verify platelets are of Cd 3 As 2 using energy-dispersive X-ray spectroscopy and crystalline surfaces using scanning electron microscopy
Use chemical vapor deposition furnace with flow rate of inert gas and optional vacuum pump to achieve lower pressures Evaporate target consisting of chunks of Cd 3 As 2 by increasing temperature beyond the evaporating points of both species. Target concentrations begin to diffuse along the tube in all directions due to pressure created by heat gradient in furnace. Flow rate of argon directs evaporated target to the right. Vapors deposit at the sublimation temperature of tube and undergo reaction and by-products exit Temperature, pressure, flow rate, reaction time variables adjusted to optimize growth Use EDX analysis to confirm platelets are Cd 3 As 2. Obtain SEM images to confirm crystallinity, obtain electron mobility Furnace end 700 °C 100 °C 25 °C 100 °C25 °C
Platelets display microscopically smooth surfaces with leaf like morphology around edges as seen from SEM images (below) Platelets are formed in various sizes ranging approximately from 1 to 5mm. Repeatable semicrystalline (smooth surface) product growth experiments occured when using the conditions of samples 11 and 12 and repeatable polycrystalline (rough surface) product growth occurred under the conditions of samples 1 through 5 High conductivity measured at 9.06X10^5 S/m with an electron mobility measured at 4158 cm^2/Vs