AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Wednesday Sessions
       Session NS-WeM

Paper NS-WeM9
Fabrication of Bismuth Nanowires with a Silver Nanocrystal Shadowmask

Wednesday, October 27, 1999, 11:00 am, Room 612

Session: Nanopatterning
Presenter: S. Choi, University of California, Los Angeles
Authors: S. Choi, University of California, Los Angeles
K. Wang, University of California, Los Angeles
M. Leung, Aerospace Corporation
G. Stupian, Aerospace Corporation
N. Presser, Aerospace Corporation
B. Morgan, Aerospace Corporation
R. Robertson, Aerospace Corporation
E. King, Aerospace Corporation
M. Tueling, Aerospace Corporation
S. Chung, University of California, Los Angeles
J. Heath, University of California, Los Angeles
S. Cho, Northwestern University
J. Ketterson, Northwestern University
Correspondent: Click to Email
There has been much interest in arrays of bismuth (Bi) nanowires for both fundamental understanding and device application because of many interesting properties such as long mean free path of the carriers and the small effectiveness and the semimetal-semiconductor transition. In this abstract, we describe a method of using silver (Ag) nanocrystal wires as a shadowmask to produce nanometer-size Bi wire patterns and discuss transport properties of Bi nanowires. In our technique, organically functionalized Ag nanocrystals (2-100nm) can assemble into lamella (wire-like) phases. The width of the wires could be controlled from 20 to 300nm. The wire patterns can be transferred as Langmuir-Scheffer (horizontal lift-off) films to the polymethyl methacrylate (PMMA) coated Bi/CdTe substrates. Bi epilayers were grown by molecular-beam epitaxy (MBE) on CdTe (111) B substrates. X-ray diffraction showed only sharp (00.l) peaks were present, which implied c-axis growth of Bi perpendicular to the substrates. Cleanness of surface of Bi films was also confirmed by the Time-Of-Flight Secondary Ion Mass Spectroscopy (TOFSIMS) using high energy Gallium ions. The wire patterns were transferred to the PMMA films by spatially selective electron beam exposure on the Ag nanocrystal wire shadowmask. 50 nm and 70 nm wide Bi wire patterns were formed by a subsequent anisotropic reactive ion etching (RIE) process. The metal contacts on the Bi nanowires were prepared by in-situ Focused Ion Beam (FIB) deposition for temperature dependent resistance measurement. In zero magnetic field, the temperature dependent resistance measurements on the Bi nanowires with widths of 50 nm and 70 nm showed the resistance increased with decreasing temperature, which was characteristic for semiconductor and insulators.