Study of Electrical Transport in Topological Thin Films/Nanowires and Device Fabrication

Ismail, Maneesha (2017) Study of Electrical Transport in Topological Thin Films/Nanowires and Device Fabrication. Masters thesis, Indian Institute Of Science Education and Research Kolkata.

PDF (MS dissertation of Maneesha Ismail (11MS035)) 11MS035.pdf - Submitted Version Restricted to Repository staff only Download (17MB)

Abstract

This thesis is broadly focused on the electrical transport study on topological thin films and nanowires with the fabrication of Bismuth Telluride (Bi₂Te₃) and optimizing electrical contacts on them an integral part of the study. It was rather challenging to get an optimized electrical contacts on Bi₂Te₃ Nanowires without high contact resistance. We have extensively discussed the problems and possible solutions to fabricate the device in this thesis. The discussion starts with the chemical preparation of Nanowires followed by the optimization of concentration and cleaning. In subsequent sessions a detailed description of Chromium - Gold contact deception on nanowires has been discussed including measurement of resistance and current across the sample as a function of temperature and voltage respectively. The rationale of the outcome led to the delineated work of contact optimization. The electrical transport of topological thin film Bi₁.₅Sb₀.₅Te₁.₇Se₁.₃(BSTS) has been performed in the first half of thesis. We have studied the electrical transport of two BSTS thin films. From the resistance measurement of this film we observed that a hump in resistance close to 200 K. We also studied the resistance fluctuations at this region of temperature and observed the resistance and fluctuation behave oppositely as a function of temperatures. The noise temperature dependent as well as bias dependent noise data has been discussed in detail. Experiment was repeated in liquid helium temperature. Further propositions and a future direction of experiments have also been discussed and justified in this thesis.

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