An advanced charge-transfer yield is demonstrated by employing single monolayers of transition-metal oxides—tungsten trioxide (WO3) and rhenium trioxide (ReO3)—deposited on the hydrogenated diamond surface, resulting in improved p-type sheet conductivity and thermal stability. Surface conductivities, as determined by Hall effect measurements as a function of temperature for WO3, yield a record sheet hole carrier concentration value of up to 2.52 × 1014 cm−2 at room temperature for only a few monolayers of coverage. Transfer doping with ReO3 exhibits a consistent narrow sheet carrier concentration value of around 3 × 1013 cm−2, exhibiting a thermal stability of up to 450 °C. This enhanced conductivity and temperature robustness exceed those reported for previously exposed surface electron acceptor materials used so far on a diamond surface. X-ray photoelectron spectroscopy measurements of the C1s core level shift as a function of WO3 and ReO3 layer thicknesses are used to determine the respective increase in surface band bending of the accumulation layers, leading to a different sub-surface two-dimensional hole gas formation efficiency in both cases. This substantial difference in charge-exchange efficiency is unexpected since both surface acceptors have very close work functions. Consequently, these results lead us to consider additional factors influencing the transfer doping mechanism. Transfer doping with WO3 reveals the highest yet reported transfer doping efficiency per minimal surface acceptor coverage. This improved surface conductivity performance and thermal stability will promote the realization of 2D diamond-based electronic devices facing process fabrication challenges.
In this paper, the Al2O3/InGaAs interface was studied by X-ray photoelectron spectroscopy (XPS) after a breakdown (BD) event at positive bias applied to the gate contact. The dynamics of the BD event were studied by comparable XPS measurements with different current compliance levels during the BD event. The overall results show that indium atoms from the substrate move towards the oxide by an electro-migration process and oxidize upon arrival following a power law dependence on the current compliance of the BD event. Such a result reveals the physical feature of the breakdown characteristics of III-V based metal-oxide-semiconductor devices.
Low resistivity (∼100 μΩ cm) titanium nitride (TiN) films were obtained by plasma enhanced atomic layer deposition using tetrakis(dimethylamido)titanium and a nitrogen/argon plasma mixture. The impact of process parameters on film crystallinity, oxygen contamination, and electrical resistivity was studied systematically. A low background pressure during the plasma half-cycle was critical for obtaining low resistivity. The low resistivity films were highly crystalline, having (001) oriented columnar grains. Oxygen and carbon content was about 3% and 2%, respectively. The role of argon plasma in film properties is discussed. Plasma damage to thin dielectric films beneath the TiN layer was minimized by the low-pressure process. The authors suggest that electron scattering at grain boundaries is the dominant mechanism which determines the resistivity of the TiN films, thus obtaining large columnar grains is the key to obtaining low film resistivity.
The authors report on the properties of various conductive nitride (TiN, ZrN, and TaN) films prepared by plasma enhanced atomic layer deposition using either quartz or sapphire inductively coupled plasma (ICP) sources. Different reactive gases (N2, NH3, and H2) and various pressures during the plasma half-cycle were examined. The sapphire based ICP source enabled higher deposition rates, better crystallization, lower film resistivity, and lower oxygen contamination. The effect of the ICP source material depends strongly on the reactive gas species and pressure. Optimal deposition conditions for both ICP source materials are determined.
The authors deposited titanium nitride (TiN) films by plasma-enhanced atomic layer deposition on various types of amorphous, polycrystalline, and single crystalline substrates and found that the crystallinity of the substrate strongly affects the morphology, orientation, and resistivity of the films. An appropriate substrate choice yields TiN films with bulk resistivity values of about ∼20 μΩ cm. The preferred crystallographic orientation of the films, either (111) or (001), does not affect film resistivity.
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