Inelastic electron tunneling spectroscopy and atomic force microscopy investigation of ultrathin sputtered amorphous silica films on gold

Abstract

Ultrathin amorphous SiO2 films are radio frequency sputter deposited onto thin film gold electrodes and incorporated as the insulating barrier in metal/insulator/metal tunnel junctions of the type Au/SiO2/Pb. Inelastic electron tunneling spectra (IETS) recorded at 4.2 K reveal characteristic zero bias anomalies associated with rapid variations in the Pb density of states on either side of the superconducting gap which shows unequivocally that tunneling is the primary conduction mechanism through the junctions at this temperature. Full IET spectra reported are essentially identical to those previously recorded for similar SiO2 films on aluminum. Atomic force and scanning tunneling microscope images of the SiO2 and underlying gold films are also presented; these data confirm that the SiO2 films are sufficiently uniform and continuous for IETS.

Inelastic Electron Tunneling Spectroscopy

“…Films can be radio frequency sputterdeposited onto thin film gold electrodes and incorporated as the insulating barrier in Au/SiO 2 /Pb junctions. 104 For many years it was thought impossible to make such tunnel junctions because the presence of small pin holes in the oxide layer would allow Au-Pb contacts to form. However, in this study IETS spectra recorded at 4.2 K reveal characteristic zero bias anomalies which show unequivocally that tunneling is the primary conduction mechanism through the junctions at this temperature.…”

Characterization of Metal Oxide Surfaces and Thin Semiconductor Films by Inelastic Electron Tunneling Spectroscopy

“…The structures and properties of these thin evaporated semiconductor films have been studied. 20,21,[103][104][105][106][107][108][109][110][111][112][113][114][115][116][117][118][119] Tunneling spectra of oxides grown on Si wafers were also reported. [120][121][122][123][124][125] …”

“…Though they studied tunneling spectra of various adsorbed species on these surfaces, detailed analysis and assignments for the species in the Si and SiO2 films were not made. Mallik et al [116][117][118] measured the tunneling spectra of the SiO and SiO2 films prepared by radio-frequency sputter deposition on Al or Au in argon. The tunneling spectra of the SiO films showed the peaks of OxSiH at 2230 and 900 cm -1 .…”

Spectroscopic, topological, and electronic characterization of ultrathin a-CdTe:O tunnel barriers

“…Several techniques have been used to investigate these processes including x-ray photoelectron a͒ Author to whom correspondence should be addressed; electronic mail: rrm@physics.uakron.edu spectroscopy, 10 and deep level transient spectroscopy. 11 In this article, we use inelastic electron tunneling spectroscopy ͑IETS͒, which been used previously to study the vibrational spectra of ultrathin sputtered films of germanium oxide, 12 silicon and its oxides, 13,14 and evaporated silicon and its oxides. 15 In this technique, inelastic scattering of electrons tunneling through a thin-film barrier in a metal/barrier/metal tunnel junction is employed to excite vibrational, optical, and electronic modes in the barrier material.…”