Studies on Al—insulator—Pb tunnel junctions with barriers prepared in glow discharge of CO2 and CO

Abstract

Al‐insulator—Pb tunnel junctions with barriers produced in a glow discharge of CO2 or CO are studied. It is shown that for the first case a barrier is similar in its composition to those prepared using the plasma oxidation technique but contains molecules of the chemisorbed formic acid. HCOOH is found to be formed due to the organic synthesis in the glow discharge. In the second case there are junctions with barriers of 0.25 to 0.3 eV height. Certain assumptions of the barrier composition are made.

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

“…6,18,30,36,[38][39][40][41][42][43][44][45][46][47][48][49][50] The tunneling spectra of formic acid on alumina and magnesia doped from the vapor are shown in Fig. 7.…”

“…The νCH peaks lie at 2880 cm -1 and the peaks at 2760 and 3000 cm -1 are the overtone of δCHin (1380 cm -1 ) and the combination mode of δCHin (1380 cm -1 ) and νasCOO -(1610 cm -1 ), respectively. 39,46 The weak peaks at 790 cm -1 are due to the deformational mode of COO -(δCOO -). The tunneling spectra of formic acid on alumina and magnesia show the 6 normal vibrational modes of the formate anion.…”

“…[45][46][47] The tunneling spectra of acetic acid and related compounds were also well investigated. 1,2,6,12,18,30,[38][39][40][42][43][44]51,52 Acetic acid is adsorbed as acetate anion on both oxide surfaces. The medium and broad peak due to νasCOO -lies at 1580 cm -1 .…”

“…The tunneling spectra of propionic acid 1,18,39,41,55 and other fatty acids 2,18,[53][54][55][56][57][58][59][60][61][62][63][64] were measured and reported. The tunneling spectra of myristic (C14), palmitic (C16), and stearic (C18) acid on alumina doped from benzene solutions (0.1 -1.0 mg/ml) are shown in Fig.…”

Reversible Molecular Adsorption and Detection Using Inelastic Electron Tunneling Spectroscopy in Monolithic Nanoscopic Tunnel Junctions

“…The O−H stretch is still present but appears at a lower frequency of 3430 cm −1 . In addition to electrode changes, differences may arise from the local molecular environment such as with hydrogen bonding . The O−H stretch again indicates the presence of physisorbed molecules, and the O−H bending band is again seen at 1151 cm −1 .…”