Amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) invented only one decade ago are now being commercialized for active-matrix liquid crystal display (AMLCD) backplane applications. They also appear to be well positioned for other flat-panel display applications such as active-matrix organic light-emitting diode (AMOLED) applications, electrophoretic displays, and transparent displays. The objectives of this contribution are to overview AOS materials design; assess indium gallium zinc oxide (IGZO) TFTs for AMLCD and AMOLED applications; identify several technical topics meriting future scrutiny before they can be confidently relied upon as providing a solid scientific foundation for underpinning AOS TFT technology; and briefly speculate on the future of AOS TFTs for display and non-display applications.

An amorphous oxide semiconductor thin-film transistor route to oxide electronics

Band structures and band offsets of high K dielectrics on Si

The comparison of simulated write/erase characteristics of silicon–oxide–nitride–oxide–silicon (SONOS) nonvolatile memory with different oxides SiO 2 , Al 2 O 3 and ZrO 2 as a top dielectric was made. We demonstrate, that an application of high- k dielectrics allows to decrease the write/erase programming voltage amplitude or programming time from 1 ms to 10 μs. The ZrO 2 suppresses parasitic electron injection from polysilicon gate. Also the design of SONOS memory based on high- k dielectrics is promising for terabit scale using hot carriers injection EEPROM and DRAM memory.

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A new low voltage fast SONOS memory with high-k dielectric

The local bonding of Zr, Si, and O atoms in plasma-deposited, and post-deposition annealed Zr silicate pseudobinary alloys [(ZrO2)x(SiO2)1−x] was studied by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Systematic decreases in XPS binding energies, and increases in AES kinetic energies with alloy composition x are consistent with an empirical chemical bonding model based on electronegativity equalization; however, there are significant departures from the predicted linear composition dependencies of that model. Deviations from linearity in the XPS compositional dependencies are correlated with dipolar network atom fields as determined from ab initio calculations. The nonlinearities in the x dependence of ZrMVV and OKVV AES spectral features are determined primarily by oxygen–atom coordination dependent shifts in valence band offset energies. The energy spread in the compositional dependence of binding energies (∼1.85 eV) for the XPS Zr 3d5/2 and Si 2p features combined with...

Nonlinear composition dependence of x-ray photoelectron spectroscopy and Auger electron spectroscopy features in plasma-deposited zirconium silicate alloy thin films

We review some recent developments in many-body perturbation theory (MBPT) calculations that have enabled the study of interfaces and defects. Starting from the theoretical basis of MBPT, Hedin’s equations are presented, leading to the GW and GWΓ approximations. We introduce the perturbative approach, that is the one most commonly used for obtaining quasiparticle (QP) energies. The practical strategy presented for dealing with the frequency dependence of the self-energy operator is based on either plasmon-pole models (PPM) or the contour deformation technique, with the latter being more accurate. We also discuss the extrapolar method for reducing the number of unoccupied states which need to be included explicitly in the calculations. The use of the PAW method in the framework of MBPT is also described. Finally, results which have been obtained using MBPT for band offsets at interfaces and for defects are presented, with emphasis on the main difficulties and caveats.

Electronic properties of interfaces and defects from many-body perturbation theory: Recent developments and applications

Characterization of ultrathin zirconium oxide films on silicon using photoelectron spectroscopy

Electronic structure and energy band offsets for ultrathin silicon nitride on Si(1 0 0)

We have measured the energy bandgaps of thermally evaporated ZrO2 on Si(1 0 0) and a very-thin interfacial silicate (SiOx:Zr) layer formed by 500 °C annealing in dry O2 from the onset of the energy loss spectra of O 1s photoelectrons. The valence band lineups at the interfaces among ZrO2, SiOx:Zr and Si(1 0 0) have also been evaluated by analyzing the valence band spectra of thin heterostructures. By combination of the measured energy bandgaps and valence band lineups, we have determined the energy band alignments of as-evaporated ZrO2/Si(1 0 0) and annealed ZrO2/SiOx:Zr/Si(1 0 0) systems. The influence of 300–500 °C O2-annealing on the energy distribution of electronic defect states in the films and at the interfaces has been demonstrated by total photoelectron yield measurements.

Chemical and electronic structure of ultrathin zirconium oxide films on silicon as determined by photoelectron spectroscopy

Microcrystalline (μc) thin films of Si 1− x Ge x :H (0.16⩽ x ⩽0.89) were prepared on quartz, Cr-evaporated Si(1 0 0) and H-terminated Si(1 0 0) by plasma-enhanced chemical vapor deposition (CVD) from SiH 4 +GeH 4 +H 2 gas mixtures with various GeH 4 /SiH 4 molar fractions and substrate temperatures. The crystallinity of the films was characterized by Raman scattering spectroscopy and transmission electron microscopy (TEM). We have demonstrated the formation of a highly crystallized and structurally relaxed Si 1− x Ge x network with nearly homogeneous composition in the temperature range 200–300 °C. However, for the deposition on quartz and Cr-evaporated Si(1 0 0), the crystallite nuclei emerge after the growth of the amorphous layer as thick as 25 nm which is markedly larger than the incubation layer thickness for μc-Si:H (typically ∼5 nm under a similar deposition condition).

M Narasaki

Papers

Characterization of ultrathin zirconium oxide films on silicon using photoelectron spectroscopy

Electronic structure and energy band offsets for ultrathin silicon nitride on Si(1 0 0)

Chemical and electronic structure of ultrathin zirconium oxide films on silicon as determined by photoelectron spectroscopy

Growth and characterization of microcrystalline silicon–germanium films☆