Browsing by Author "Pande, Krishna P."

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Growth and Crystal Structure Investigation of InAs/GaSb Heterostructure Nanowires on Si Substrate
(2018-11-01)
Kakkerla, Ramesh Kumar
;
Hsiao, Chih-Jen
;
Anandan, Deepak
;
Singh, Sankalp Kumar
;
Chang, Sheng-Po
We report gold-free growth of vertically aligned InAs/GaSb heterostructure nanowires (NWs) on Si(111) substrate by metal organic chemical vapor deposition technique. The effect of growth temperature on morphology and growth rate for InAs and InAs/GaSb heterostructure NWs were investigated. A combination of high material flow rates and optimum temperature (600 degrees C) has given better crystal quality of InAs nanowires. The morphology and shell thickness of NWs as observed by scanning electron microscope and transmission electron microscope (TEM) measurements can be tuned by the growth temperature. Electron microscopy also shows the formation of GaSb both in radial and axial directions outside the InAs NW core at certain growth temperatures. Crystal structure of InAs and InAs/GaSb heterostructure NWs was analyzed by high-resolution TEM and fast Fourier transform analysis. Using good crystalline InAs core grown at optimized growth temperature (600 degrees C), GaSb shell has been grown without any misfit dislocations at the core-shell interface. Basic electrical properties have been measured by forming ohmic contacts. I-V characteristics exhibit linear response indicating good ohmic behavior. These results show good control over InAs NWs growth, the GaSb shell thickness, and its crystal quality, which are essential for future nanoelectronic devices such as tunneling FET.
Synthesis of Wafer-Scale WSe2 by WOx Selenization on SiO2 / Si Substrates
(2016)
Chu, Yung-Ching
;
Jong, Chao-An
;
Ho, Yen-Teng
;
Zhang, Ming
;
Chien, Po-Yen
Scalable synthesis of thin tungsten diselenide (WSe2) films on 4-inch silicon substrate with 80 nm silicon dioxide (SiO2) is demonstrated. Cross-sectional transmission electron microscopy (TEM) reveals good control of WSe2 layers. Raman spectroscopy confirms high quality crystal of WSe2 is achieved. Back-gated field-effect transistors (FETs) fabricated on these thin films exhibit p-channel characteristics with a good on/off current ratio larger than 1.2 x 10(2).