Field Electron Emission from GaAs Nanowhiskers Fabricated by MBE

摘要

Semiconductor nanowhiskers (NWs) are wire-like nanocrystals with high (10-100) lendth/diameter ratio and the diameter of several tens of nanometers. Unique structural properties of NWs make them very attractive in numerous applications including optoelectronics, microelectronics, field emission devises and analytical chemistry [1]. Investigations on the electron emission properties of self-assembled GaAs NWs (Fig. 1) included measurements of the electron emission current (Ie) dependences on the potential difference (Ve) in the vacuum gap between the probe tip and GaAs NWs "surface". The electron emission properties of a selected ensemble of nanowhiskers were studied in a certain local microareas (with linear dimensions of ～10μm) which was defined prior to measurements of current-voltage characteristics (CVC) of the GaAs surface using a high-vacuum SPM mounted in the LS SPM unit ("OMICRON" Company, German). Note that the surface density of GaAs crystalline nanostructures growth on the substrate surface by MBE technique was ～10{sup}9 cm{sup}(-2). To study electron emission properties of the nanostructures, spatial scanning involved measurement of the CVCs. To this end, a saw tooth voltage was applied between the probe and the substrate during scanning, which was varied from some initial value V{sub}o to the maximum value V{sub}m. Note that the full probe displacement was carried out in a sequence of steps, with emission current I{sub}e versus voltage measurements (at fixed probe positions) at each step. The measured local CVCs (see figs. 2, 3) were stored in the RAM memory of PC and (after averaging) were displayed on the LS SPM unit monitor screen.