D. Zeller

Electron injection from n-type Si substrates into (i) Transition metal high-k dielectrics and (ii) SiO 2 and Si oxynitride alloys: Conduction band edge states and negative ion state electron trap differences

The limiting performance and reliability of metal-oxide-semiconductor (MOS) devices is determined by intrinsic bonding defects. These are primarily O-atom vacancies. A universal model, developed initially for (i) nano-crystalline transition metal (TM) Oxides is extended to O-vacancies in (i) non-crystalline SiO2 and Si oxynitride alloys. Differences between electron injection into, and trapping ay O-vacancy states in SiO2 and TM oxides are correlated with differences in wave function symmetries of conducition band edge electronic states.

Noncrystalline SiO2 and GeO2: Process induced pre-existing defects and vacated O-atom intrinsic bonding sites

Electron spin resonance (ESR) studies on bulk-quenched, noncrystalline (nc-) silica glasses (henceforth, nc-SiO2) have distinguished between (1) pre-existing process-induced defects introduced either after growth or annealing at high temperatures and (2) x-ray or γ-ray radiation or energetic electron particle-created defects. The ESR activity in these pre-existing defects is activated by x-rays. Similar pre-exiting defects have been demonstrated for remote plasma-deposited thin films of nc-SiO2 and nc-GeO2. Concentrations of pre-existing defects increase exponentially with increasing quenching and annealing temperatures. This is always the case for so-called “dry silicas” with no detectable Si–OH bonding. Nonbonding O-hole centers or nonbonding O-associated hole centers are also detected in dry silicas but only after significant x-ray, γ-ray, or energetic electron irradiation. Pre-existing defect has also been detected by second derivative O K pre-edge x-ray absorption spectroscopy in thermally grown and ...

Process induced pre-existing defects in non-crystalline SiO2 and GeO2 at vacated O-atom bonding sites and comparisons with Ge-S(Se) alloy bonding sites

Three related topics are addressed in this article: (i) X-ray spectroscopy (XAS) studies of remote plasma deposited (RPD) nc-SiO2 and nc-GeO2 emphasizing (a) band-edge states and (b) pre-existing bonding defects; (ii) interpretation of X-ray absorption and photoemission spectra based on many electron theory, and in particluar charge transfer multiplets (CTs); and (iii) band-edge electronic structure and intrinsic defects in nc-SiO2 and nc-GeO2 thin films and their interfaces with Si and Ge substrates. The most significant result is the identification of local atomic structure in medium range order (MRO) clusters in which the pre-existing defects are embedded. These defects are vacated O-atom sites in which O-atoms have never been resident. They are confined to 1 nm scale chemically-ordered clusters distributed non-periodically with quartz-structured 4-fold coordinated Si(Ge) and 2-fold coordinated O bonding in 12-atom regular rings. Vacated O-atom sites defects are formed during processing and annealing, and reducing macroscopic as well as local bond-strain strain. They are qualitatively different, and readily distinguished from defects introduced by electrical, and by X-ray, γ-ray or high energy electron stressing of nc-SiO2 and nc-GeO2.

X-ray absorption studies of elemental and complex transition metal (TM) oxides: Differences between: (i) Chemical, and (ii) Local site symmetry multivalency

Alloy induced multivalency in transition metal oxides increases device functionality. Effects include insulator to metal transitions in the d⁰ perovskites (i) GdScO<inf>3</inf>, by substitution of tetravalent Ti trivalent for Sc, and (ii) LaMnO<inf>3</inf> by alloy substitution of trivalent La and divalent Sr for trivalent La. Substituion of Ti³⁺ for Sc³⁺ on the ScO<inf>2</inf> planes leads to hopping induced multivalencey for both Ti and Sc, but only for Ti compositions above a percolation threshold. The formation of La<inf>1−x</inf>Sr<inf>x</inf>MnO<inf>3</inf> alloys leads to mixed valence of the Mn-atoms: Mn³⁺ in the LaMnO<inf>3</inf> fraction, and Mn⁴⁺ in the SrMnO<inf>3</inf> fraction. Spectroscopic detection is based on charge transfer multiplet theory applied to Ti, Sc and Mn L<inf>2,3</inf> spectra were multivalent charge states increase the number of spectral features. Multivalency also occurs suboxide alloys such as TiO<inf>2−x</inf> in a composition range: TiO<inf>2</inf> > TiO<inf>2−x</inf> > TiO<inf>1.5</inf>. These alloys have a mix of Ti⁴⁺ and Ti³⁺ local bonding states, but due to hopping transport, the mix includes Ti²⁺. One important aspect of controlled multivalency is that it provides a way of changing and/or controlling the density of O-vacancy defects. Electrons can be injected into the oxide negative ion states ion states from Si, Ge, and other semiconductors, as well as metals with different offset energies [1]. The two terminal devices with asymmetric current-voltage charateristics providing options for memory devices.