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Investigation of single InP nanowires and CdS nanosheets by using photocurrent and transport spectroscopy

Maharjan, Amir M.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258658812

Abstract Details

2009, PhD, University of Cincinnati, Arts and Sciences : Physics.
In this work we use photocurrent and transport spectroscopes to invenstigate an optoelectronic properties of single InP nanowire and single CdS nanosheet both at room temperature and low temperature. Photolithography is used to fabricate the Ti/Al metal contact pads separated by 3-5 microns on several InP nanowires and CdS nanosheet devices. Back to back metal semiconductor metal (MSM) contacts are modeled based on thermionic emission theory and thermionic field emission theory .These are used to explain the dark I-V characteristics of these nanostructures which enables measurement of the important intrinsic properties including donor density, barrier heights and electrical conductivity of nanostructures. We have used photocurrent spectroscopy of single InP nanowires at room temperature and low temperature to study nanowires having either zincblende(ZB) or wurtzite (WZ) crystal structures. Current-voltage (I-V) photocurrent characteristics of a nanowire are obtained by broad illumination of the device from a Ti-Sapphire laser with energies ranging from 1.30eV to 1.55eV.The photocurrent at a given bias voltage is plotted as a function of photon energy to determine the band edge of given semiconductor nanowire. The photocurrent drops exponentially below the band edge reflecting Urbach's rule. We find that the energy band gap of wurzite (WZ) phase nanowire is about 70meV greater than the zincblende (ZB) phase nanowires at room temperature is in agreement with the recent photoluminescence (PL) measurements. It shows that the photocurrent spectroscopy can clearly distinguish ZB and WZ structures. Since photocurrent measurement needs lot less power of light and can be used even at room temperature, photocurrent spectroscopy tool can become a very cheap and rapid means of characterizing the nanostructures such as nanowires ,nanotubes and nanosheets. At low temperature we observe an exciton like peak in photoresponse of ZB InP nanowire and find the binding energy of exciton is ~5meV at 10K, in agreement with the recent PL experiments. The scanning photocurrent microscopy (SPCM) of single InP nanowire and single CdS nanosheet shows that the peak photocurrent always appears at the reverse (negative) contact of the MSM nanowire device revealing that the photoresponse has strong spatial inhomogeneity. We present two different charge carrier mechanisms in nanowires in terms of the mobility of the charge carriers and space charge limited current (SCLC). The polarization photocurrent measurement on single CdS nanosheet shows that the c-axis is almost perpendicular to the long axis of the nanosheet.
Andrei Kogan, PhD (Committee Chair)
Leigh Smith, PhD (Committee Member)
Michael Ma, PhD (Committee Member)
Alan Schwartz, PhD (Committee Member)
142 p.
Condensation
photocurrent spectroscopy; transport spectroscopy; InP nanowires; photocurrent; CdS nanowires

Recommended Citations

Citations

  • Maharjan, A. M. (2009). Investigation of single InP nanowires and CdS nanosheets by using photocurrent and transport spectroscopy [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258658812

    APA Style (7th edition)

  • Maharjan, Amir. Investigation of single InP nanowires and CdS nanosheets by using photocurrent and transport spectroscopy. 2009. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258658812.

    MLA Style (8th edition)

  • Maharjan, Amir. "Investigation of single InP nanowires and CdS nanosheets by using photocurrent and transport spectroscopy." Doctoral dissertation, University of Cincinnati, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258658812

    Chicago Manual of Style (17th edition)

ucin1258658812
719
© 2009, some rights reserved.Creative Commons License Investigation of single InP nanowires and CdS nanosheets by using photocurrent and transport spectroscopy by Amir M. Maharjan is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.