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Traditional application of multipactor coatings applied with sputtering techniques to high-power RF windows typically performs well when applied to sintered powder ceramics. Unfortunately, sputtered coatings do not adhere well to crystal materials, such as sapphire. This publication describes a plasma-assisted process that molecularly bonds the multipactor coating to the base window material. The performance was verified by measuring secondary electron emission yield and operating the window at high power. The coating process and performance are presented.

Remote plasma processing (RPP) provides pathways to the formation of photovoltaic (PV) and thin-film-transistor (TFT) devices that include buried interfaces. This is made possible by separate and independent control of (i) plasma excited O- and N-atom deposition precursors in a up-stream plasma chamber, combined with (ii) down-stream injection of Si- and Ge-atoms with control gas flow rates providing control of buried interface bonding at monolayer levels. Devices with intrinsic, B p-type and P n-type “a-Si(H)” & “a-Si,Ge(H)” layers require 10% bonded H in monolayer (Si H arrangements) and deposition and/or annealing at temperatures between 240 and 275 °C. Deposition from SiH4 with either PH3 or B2H6 dopant gasses provides spectrally reflecting films which can be annealed yielding fine-grain films for gate, or source and drain regions for TFTs or FETs.

Ge interface nitride passivation.Si passivation layer thickness.SiON surface on Si passivation layer.Anneal to eliminate Ge-N bonds.Symmetric NMOS and CMOS capacitors. Three significant issues with respect to the ultimate scaling limitations of CMOS devices are (i) the channel or transport material, (ii) high-? compatible gate stacks: (a) the interface with the semiconductor substrate; (b) the high dielectrics, and (c) the gate metal, and (iii) the topological structure, planar, nano-tube, or in, etc. Two of these are high-lighted, focusing on (i) crystalline Ge, and transition metal dielectrics including specifically non-crystalline Hf Si oxynitrides, and nano-grain (a) ultra-thin 2nm thick HfO2 and TiO2. The research has demonstrated shallow trap interfacial slow trap densities of ~5i?1010cm-2, no detectable negative bulk fixed charges, and symmetric N- and P-MOCAPS in planar geometries. EOT values

Performance and reliability in semiconductor devices are limited by electronically active defects, primarily O-atom and N-atom vacancies. Synchrotron X-ray spectroscopy results, interpreted in the context of two-electron multiplet theories, have been used to analyze conduction band edge, and O-vacancy defect states in nano-crystalline transition metal oxides, e.g., HfO2, and the noncrystalline dielectrics, SiO2, Si3N4 and Si-oxynitride alloys. Two-electron multiplet theory been used to develop a high-spin state equivalent d2 model for O-vacancy allowed transitions and negative ion states as detected by X-ray absorption spectroscopy in the O K pre-edge regime. Comparisons between theory and experiment have used Tanabe-Sugano energy level diagrams for determining the symmetries and relative energies of intra-d-state transitions for an equivalent d2 ground state occupancy. Trap-assisted-tunneling, Poole-Frenkel hopping transport, and the negative bias temperature instability have been explained in terms of injection and/or trapping into O-atom and N-atom vacancy sites, and applied to gate dielectric, and metal-insulator-metal structures.

Only two of the first row transition metals have elemental oxides that are either ferro- or ferri-magnetic. These are CrO2 and Fe3O4. The electron spin alignment that promotes the ferro(i)magnetism is associated with a double exchange mechanism that requires mixed valence as well as metallic conductivity. This paper describes a novel way to realize these two necessary, but not sufficient conditions for double exchange magnetism. These are mixed valence and a hopping conductivity that promotes at least intra-plane electron spin alignment in a complex oxide perovskite host, A(B,C)O3. A is an ordinary metal, or a rare earth atom, B is a d0 transition metal, and C is a d(n) transition metal in which n > or = 1, as for example in GdSc1-xTi(x)O3. This article combines X-ray absorption spectroscopy, multiplet theory, charge transfer multiplet theory and degeneracy removal by Jahn-Teller effect mechanisms to demonstrate mixed valence for both Sc and Ti above a percolation threshold, x > 0.16, in which hopping transport gives rise to a metal to insulator transition.

Non-crystalline GeO2 films remote were plasma deposited at 300 degrees C onto Ge substrates after a final rinse in NH4OH. The reactant precursors gas were: (i) down-stream injected 2% GeH4 in He as the Ge precursor, and (ii) up-stream, plasma excited O2-He mixtures as the O precursor. Films annealed at 400 degrees C displayed no evidence for loss of O resulting in Ge sub-oxide formation, and for a 5-6 eV mid-gap absorption associated with formation of GeOx suboxide bonding, x < 2. These films were stable in normal laboratory ambients with no evidence for reaction with atmospheric water. Films deposited on Ge and annealed at 600 degrees C and 700 degrees C display spectra indicative of loss of O-atoms, accompanied with a 5.5 eV absorption. X-ray absorption spectroscopy and many-electron theory are combined to describe symmetries and degeneracies for O-vacancy bonding defects. These include comparisons with remote plasma-deposited non-crystalline SiO2 on Si substrates with SiON interfacial layers. Three different properties of remote plasma GeO2 films are addressed comparisons between (i) conduction band and band edge states of GeO2 and SiO2, and (ii) electronic structure of O-atom vacancy defects in GeO2 and SiO2, and differences between (iii) annealing of GeO2 films on Ge substrates, and Si substrates passivated with SiON interfacial transition regions important for device applications.

The paper uses remote plasma assisted deposition, oxidation and nitridation processes for depositing thin films of metallic TiN on crystalline sapphire (0001) substrates. These films on sapphire substrates are being studied as window materials for high power radio frequency (RF) power tubes. A sequence of four process steps has been performed in a reactor chamber that isolates the deposition and surface-processing chamber from the plasma generation region. The chamber is part of an ultra-high-vacuum (UHV) compatible multi-chamber cluster in which the sequence of four process steps can be interrupted after each step, and surface chemistry changes can be identified by in-line Auger electron spectroscopy (AES). The four process steps, performed after an ex-situ chemical clean and blow-dry in nitrogen gas, are (i) a remote plasma-assisted oxidation (RPAO) in which surface contaminants including adventitious carbon are removed; (ii) a remote plasma-assisted nitridation (RPAN) process which forms a superficial layer of generic AION used to increase surface adhesion of the TiN films; (iii) a remote plasma-enhanced chemical-vapor deposition (RPECVD) process for deposition of 2 to 5 nm thick TiN films, and finally (iv) a second RPAN step that increases the ratio of Ti-N bonding in the TiN films with respect to adventitious O-atom incorporation from the Ti precursor, Ti tetra-butoxide.

Exposure to radiation poses significant challenges for electronic devices, including parametric degradation, loss of data, or catastrophic failure. The challenges and solutions change significantly as new materials are introduced and feature sizes become smaller. This paper reviews the effects of radiation on electronics, with emphasis on the impact of new materials.

The stability of the tetragonal phase of Ge doped HfO2 thin films on Si(100) was investigated. Hf(Ge)O2 films with Ge atomic concentrations varying from 0% to 15% were deposited by remote plasma chemical vapor deposition. The atomic structure on the oxide after rapid thermal annealing was investigated by x-ray absorption spectroscopy of the O and Ge K edges and by Rutherford backscattering spectrometry. The authors found that Ge concentrations as low as 5 at. % effectively stabilize the tetragonal phase of 5 nm thick Hf(Ge)O2 on Si and that higher concentrations are not stable to rapid thermal annealing at temperatures above 750 °C.

The white line and X-ray absorption near edge spectros-copy (XANES) spectral regions of the Ge K edge, ∼11100 to 11112 eV, and between 11112 and 11180 eV and beyond, contain electronic structure information that complements near-neighbor bonding information in the single-scattering EXAFS regime. The multiple-scattering XANES features are not generally addressed in EXAFS studies that are targeted to obtain bonding information. There are systematic changes in the X-ray photon energy of the spectral peak of the white line for Ge-Sb-Te (GST) alloys, GeSb and GeTe model compounds, and other Ge alloys that scale directly with average bond ionicity. The spectral widths of these features correspond tp electronic transitions important in optical memory devices. There are other features in the XANES region associated with shake-off effects for shallow atomic core states that re-veal bonding information important in analysis of the oscillatory features in the EXAFS regime. These include bonding pairs that are addressed in the fit procedures; e.g., Ge-Te and Ge-Sb in GST 225. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This article addresses three different aspects of nano-scale structure that are important for the implementation of high-k gate dielectrics, such as HfO2 and Hf Si oxynitride alloys, for advanced gate stack applications ultra large scale integrated (ULSI) circuit and system chips. Two of these deal with nano-crystalline thin films where it is necessary to make a distinction between the primitive unit cell, and a more extended electronic cell that can support cooperative Jahn-Teller distortions. The final example relates the bonding coordination of group IVB transition metal (TM) atoms, Ti, Zr and Hf in a ternary composition in which the concentration of four-fold coordinated TM atoms is above a critical percolation threshold. This is critical for strain relief, thereby promoting low densities of electronically-active defects. X-ray absorption spectroscopy studies play a significant role in revealing these important aspects of nano-structure, and are interpreted with in the frame-work of many-electron electronic structure theory. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This article analyzes results from two papers that have studied the first sharp diffraction peak, FSDP, in GexSe1-x alloys as a function of the alloy composition, x. The research reported in one of these papers obtained the FSDP in eighteen closely spaced compositions for x between 0.15 and 0.4, and included the intermediate phase, IP, regime between x = ∼0.2 and ∼0.25. S(Q) structure factor plots from diffraction measurements were characterized empirically in terms with several different fitting functions. These second paper used Monte-Carlo methods for a smaller set of compositions. In this paper, the positions and widths of the FSDP's peaks as a function of alloy composition are correlated with changes in the atomic bonding from Se-rich to Ge-rich regimes. Additionally this paper identifies medium range order, MRO, length scales for chemical bonding self-organizations within the IP regime that are important for promoting macroscopic strain reduction. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This article identifies a length scale for spinodal decomposition of Hf and Zr silicate alloys. This has provided important insights into chemical bonding self-organizations in non-crystalline alloys as well, in particular for the intermediate phase regime of chalcogenide alloys. Additional insights into nanolength scales for chemical bonding self-organizations; also extending into the medium range order (MRO) regime in network glasses are identified through comparisons between the first sharp diffraction peaks in oxide and chalcogenide compounds and alloys. These length scales are based on the extraction of real space correlation and coherence lengths, R and L, respectively. These comparisons have identified bond-ionicity related differences in the short range order which play a significant role in promoting differences in MRO between oxides and chalcogenides, including bulk glasses as well as thin films.

This paper distinguishes between two different scales of medium range order, MRO, in non-crystalline SiO2: (1) the first is ~0.4 to 0.5 nm and is obtained from the position of the first sharp diffraction peak, FSDP, in the X-ray diffraction structure factor, S(Q), and (2) the second is ~1 nm and is calculated from the FSDP full-width-at-half-maximum FWHM. Many-electron calculations yield Si–O third- and O–O fourth-nearest-neighbor bonding distances in the same 0.4–0.5 nm MRO regime. These derive from the availability of empty Si dπ orbitals for back-donation from occupied O pπ orbitals yielding narrow symmetry determined distributions of third neighbor Si–O, and fourth neighbor O–O distances. These are segments of six member rings contributing to connected six-member rings with ~1 nm length scale within the MRO regime. The unique properties of non-crystalline SiO2 are explained by the encapsulation of six-member ring clusters by five- and seven-member rings on average in a compliant hard-soft nano-scaled inhomogeneous network. This network structure minimizes macroscopic strain, reducing intrinsic bonding defects as well as defect precursors. This inhomogeneous CRN is enabling for applications including thermally grown ~1.5 nm SiO2 layers for Si field effect transistor devices to optical components with centimeter dimensions. There are qualitatively similar length scales in nano-crystalline HfO2 and phase separated Hf silicates based on the primitive unit cell, rather than a ring structure. Hf oxide dielectrics have recently been used as replacement dielectrics for a new generation of Si and Si/Ge devices heralding a transition into nano-scale circuits and systems on a Si chip.

This article addresses O-atom vacancy defects in the d 0 transition metal (TM) oxides HfO 2 and TiO 2 , and Ti substitutions for Sc in the d 0 complex oxide GdScO 3 . In each instance this results in occupied TM atoms with d 1 state representations. These are important for different aspects of the ultimate scaling limits for performance and functionality in nano-scale Si devices. The occupancy of d 1 states is cast in terms of many-electron theory in order to determine the effects of correlation on device performance and functionality. The first section of this article identifies equivalent d-state representations using on an ionic model for the effective valence states of Ti and Hf atoms bordering on O-atom vacancy defects. Removal of an O atom to create a neutral vacancy; this is equivalent to the bonding of two electrons to each vacancy site. This give rise to two coupled d 1 states for a mono-vacancy defect. Transitions from these occupied states generate spectroscopic features in the (i) pre-edge shake-up, and (ii) virtual bound state (VBS) shake-off energy regimes in O K edge XAS spectra. The number of states confirm that these are mono-vacancy defects. The second section addresses incorporation of Ti tetravalent impurities into trivalent GdScO 3 , forcing Ti into a Ti 3+ state and generating a d 1 electronic structure. Vacancy defect concentrations in HfO 2 are generally 19 cm −3 . However, the Ti solubility in GdScO 3 is higher, and relative concentrations in excess of 16–17% lead to an insulator to metal transition with a ferri-magnetic electronic structure.

This article is dedicated to Professor Walter Spear and the many contributions he has made to the physics of transport phenomena in non-crystalline solids, including the development of the time of the flight technique for determining drift mobilities and trapping life-times in non-crystalline insulating and semiconducting solids. This technique has been applied to non-crystalline chalcogenides, including amorphous selenium (a-Se) and a-As–Se alloys, as well as a-Si, hydrogenated a-Si (a-Si:H) and microcrystalline silicon (μc-Si, more recently described as nanocrystalline, i.e. nc-Si). The thin-film materials addressed in this article have found applications in markedly different device technologies, and in each instance the research contributions of Professor Spear and his collaborators, initially at Leicester, and subsequently at Dundee, have played a significant role in providing a science base for understanding carrier transport and other properties that underpin device performance and reliability.

Transitions into, and out of intermediate phases (IPs) with minimal strain have been identified to date by Boolchand and co-workers, in bulk glasses, primarily by the extraordinary low values of the change in enthalpy, ΔHnr, associated with non-reversible heat flow, and by Lucovsky and coworkers in deposited thin films, and at dielectric–semiconductor interfaces by combining spectrographic characterizations, primarily synchrotron X-ray absorption and X-ray photoemission, and electrical measurements. This paper emphasizes chemical bonding self-organizations that minimize macroscopic strain within the IP windows, and identifies for the first time the necessary and sufficient conditions for IP windows to open, and to close, as a function of changes in the alloy composition. Percolation theory, and in particular competitive and synergistic double percolation provide a quantification of IP window first and second transition compositions that account for many of the experimentally determined IP window threshold transitions and IP window widths identified to date.

The first sharp diffraction peak (FSDP) in the structure factor, S(Q), obtained from X-ray and neutron diffraction data, is a characteristic feature of oxide and chalcogenide glasses. This feature reflects intermediate, or medium range order (MRO), and is expressed in terms of two experimentally determined parameters, the position, Q 1 (A -1 ), and the full-width at half-maximum (FWHM), ΔQ 1 (A -1 ), of the FSDP peak. These parameters determine a correlation length R=2π/Q 1 (A -1 ) and a coherence length L=2π/ΔQ 1 (A -1 ) that result from symmetry-determined contributions to the fundamental electronic structures of SiO 2 and GeSe 2 . Narrow distributions of third neighbor Si-O and Ge-Se pair correlation distances are forced by strongly correlated symmetries of Si and Ge d-states connected through intervening O and Se atoms, as well as Se inter-atom lone-pair repulsions in GeSe 2 . The local bonding of threefold coordinated B-atoms in B 2 O 3 is planar rather than tetragonal and a similar O 2pπ-B 3dπ overlap is symmetry forbidden. Instead symmetry allowed O 2pπ-B 3pπ bonding interactions play the determining role in promoting second-neighbor B-O atom coupling through intervening O-atoms, thereby extending the correlation length scale into the MRO regime.

Defect state features have been detected in second derivative O K edge spectra for thin films of nano-crystalline TiO"2 and HfO"2. Based on soft X-ray photoelectron band edge spectra, and the occurrence of occupied band edge 4f states in Gd(Sc,Ti)O"3, complementary spectroscopic features have been confirmed in the pre-edge ( 545eV) regimes of O K edge spectra. Qualitatively similar spectral features have been obtained for thin films of HfO"2 and TiO"2, and these have been assigned to defect states associated with vacancies. The two electrons/removed O-atom are not distributed uniformly over the TM atoms defining the vacancy geometry, but instead are localized in equivalent d-states: a d^2 state for a Ti monovacancy and a d^4 state for a Hf divacancy. This new model for electronic structure provides an unambiguous way to differentiate between monovacancy and divacancy arrangements, as well as immobile (or fixed) and mobile vacancies.

Three different Hf oxide based dielectrics have emerged as viable candidates for applications in advanced ULSI devices. This article focuses on two of these: (i) phase separated Hf silicates with (i) 70-85% nano-crystalline HfO"2 with a nano-grain size

Temperature and electrical stress induced degradation in the characteristics is reported for germanium substrate MOS capacitors with HfO2/HfSiON gate dielectrics. The accumulation capacitance decreases with temperature stress due to diffusion of germanium into the high-κ dielectric. The interface trap and border trap densities decrease due to temperature stress-induced oxide growth at the oxide-germanium interface.

There are many applications for nanocrystalline thin films in optical devices that require isotropic optical properties. A novel way to obtain these isotropic properties for the index of refraction and/or optical absorption constant, etc., and at the same time to minimize microscopic strain is presented in this article. This approach is based on strain reduction mechanisms that occur in the intermediate phases, IPs, of non-crystalline glasses and thin films. In these compositional regimes, either site percolation, or volume percolation, each above an applicable critical value, provides a quantitative understanding of the microscopic bonding arrangements associated with strain-reducing chemical bonding self-organizations. A similar framework, presented for the first time in this article, develops a microscopic understanding of macroscopic strain reduction in several different phase-separated composites. This understanding has emerged from focussed research on qualitatively different hetero-structure device structure constituents, e.g.; (i) high-k replacement dielectrics for SiO z in field effect transistors gate stacks for ad - vanced semiconductor devices, and (ii) active and passive thin films for optically switched memory cells. In each instance strain reduction and its intrinsic relationship to low densities of defects and defect precursors has provided a driving force in the identification of a narrow range of compositions that satisfy technological needs.

Alloy compositions for a first transition (1) into, and a second transition (2) out of intermediate phases (IPs) have been identified (i) by Boolchand and co-workers in bulk glasses, primarily by low values for the change in enthalpy, ΔH nr , for non-reversible heat flow at the glass transition temperature, and (ii) by Lucovsky and coworkers in deposited thin film by combining spectrographic and electrical studies. This paper emphasizes chemical bonding self-organizations that minimize macroscopic strain within IP windows, identifying necessary and sufficient conditions for IP windows to open, and to close. Percolation theory, competitive and synergistic double percolation, provide a framework for determining alloy compositions for the first and second transitions of IP windows in bulk glasses and thin films as well.

The contribution from a relatively low-K SiON (K~6) interfacial transition region (ITR) between Si and transition metal high-K gate dielectrics such as nanocrystalline HfO"2 (K~20), and non-crystalline Hf Si oxynitride (K~10-12) places a significant limitation on equivalent oxide thickness (EOT) scaling. This limitation is equally significant for metal-oxide-semiconductor capacitors and field effect transistors, MOSCAPs and MOSFETs, respectively, fabricated on Ge substrates. This article uses a novel remote plasma processing approach to remove native Ge ITRs and bond transition metal gate dielectrics directly onto crystalline Ge substrates. Proceeding in this way we identify (i) the source of significant electron trapping at interfaces between Ge and Ge native oxide, nitride and oxynitride ITRs, and (ii) a methodology for eliminating native oxide, or nitride IRTs on Ge, and achieving direct contact between nanocrystalline HfO"2 and non-crystalline high Si"3N"4 content Hf Si oxynitride alloys, and crystalline Ge substrates. We then combine spectroscopic studies, theory and modeling with electrical measurements to demonstrate the relative performance of qualitatively different nanocrystalline and non-crystalline gate dielectrics for MOS Ge test devices.

This paper presents a spectroscopic study of interfacial bonding and substrate gate dielectric reactions for crystalline Ge-high-K gate dielectric hetero-structures. A novel processing sequence has been developed for i) depositing HfO2 and Hf Si oxynitrides (HfSiON) onto N-passivated Ge(111) and (100) substrates in an attempt to prevent subcutaneous oxidation of the Ge substrate during dielectric deposition, and then ii) eliminating these Ge-N interfacial bonds during 650-800°C rapid thermal annealing in Ar. This approach has been motivated by previous spectroscopic studies which have demonstrated that the band-gaps of GeO2 and Ge3N4 are reduced with respect to their Si counterparts, and cannot be used as interfacial layers (ILs) on n-type Ge substrates, or in n-metal oxide semiconductor field effect transistors (n-MOSFETs) in which a p-type Ge substrate has been inverted. Changes in interface bonding as a function of post-deposition annealing for Ge/HfO2 and HfSiON, and HfO2/HfSiON stacks have been studied by X-ray absorption and photoelectron spectroscopies, revealing i) intrinsic, or pre-existing conduction and valence band edge defects, and ii) process-induced changes in band edge defects as well. [DOI: 10.1380/ejssnt.2009.381]

A study of changes in nano-scale morphology of thin films of nano-crystalline transition metal (TM) elemental oxides, HfO2 and TiO2, on plasma-nitrided Ge(100) substrates, and Si(100) substrates with ultra-thin (∼ 0.8 nm) plasma-nitrided Si suboxide, SiOx, x 150 eV is critical for this approach.

Defect states in the form of band edge electron and hole traps in HfO2 nano-crystalline films are qualitatively different in two different length scale regimes. For grain sizes > 3–4 nm, they are discrete band edge states associated with O-atom vacancies pinned and clustered at grain boundaries, whereas in as-deposited films, and films with a physical thickness of ~ 2 nm, they are band-tail defects with a density reduced by more than an order of magnitude. Defect states in non-crystalline high Si3N4 content Hf Si oxynitride alloys are qualitatively different than those in the either regime of nano-crystallinity, but instead are similar to those in SiO2, with densities 1012 cm− 2 in films with nano-grains > 3–4 nm.

This paper presents a spectroscopic study of interfacial bonding and substrate gate/dielectric reactions for crystalline Ge-high-K gate dielectric hetero-structures. A novel processing sequence has been developed for (i) depositing HfO2 and Hf Si oxynitrides (HfSiON) onto N-passivated Ge(111) and (100) substrates, designed to prevent subcutaneous oxidation of the Ge substrate during dielectric deposition, and then (ii) eliminating N from Ge-N interfacial bonds during 650-800oC rapid thermal annealing in Ar. This approach has been motivated by spectroscopic studies that have shown that the band-gaps of GeO2 and Ge3N4 are reduced with respect to their Si counterparts and cannot be used as interfacial layers (ILs) either: (i) on n-type Ge substrates, or (ii) in n-MOSFETs in which a p-type Ge substrate is inverted. Changes in interface bonding as a function of post-deposition annealing for G/HfO2 Ge/HfSiON, and Ge/HfSiON/HfO2 stacks have been studied by X-ray absorption and photoelectron spectroscopy revealing (i) conduction and valence band edge defects, as well as (ii) significant process induced changes in these defect densities.

The contribution from relatively low-K SiON interfacial transition regions (ITRs) between Si and transition metal (TM) gate dielectrics places a significant limitation on equivalent oxide thickness (EOT) scaling for Si complementary metal-oxide-semiconductor (CMOS) devices. This limitation is equally significant and limiting for Ge CMOS devices. Low-K Ge-based ITRs in Ge devices have also been shown to limit performance and reliability, particular for n-MOS field effect transistors. This article identifies the source of significant electron trapping at interfaces between n-Ge or inverted p-Ge, and Ge oxide, nitride and oxynitride ITRs. This is shown to be an interfacial band alignment issue in which native Ge ITRs have conduction band offset energies smaller than those of TM dielectrics, and trap electrons for negative Ge substrate bias. This article also describes a novel remote plasma processing approach for effectively eliminating any significant native Ge ITRs and using a plasma-processing/annealing process sequence for bonding TM gate dielectrics directly to the Ge substrate surface.

This paper identifies different length scales, λ s , for strain-reducing chemical bonding self-organizations in non-crystalline and nano-crystalline thin films. Length scales have been identified through spectroscopic studies, thermal heat flow measurements, and are analyzed by semi-empirical bond-constraint theory (SE-BCT) and symmetry adapted linear combinations (SALC) of atomic states. In both instances, strain-reducing self-organizations result in reduced defect densities that are minimized and enabling for device applications. The length scale for non-crystalline solids extends to at most 1 nm, and more generally to 0.5–0.8 nm; however, there are two different length scales for nano-crystalline films: one is 3–3.5 nm and defines a regime where complex unit cells, comprised of two or more primitive unit cells are stabilized and the electronic structure is changed.

Bond constraint theory provides insights into glass and intermediate phase formation in covalently-bonded non-crystalline networks. Metrics are the average number of bonds/atom, N av , and average number of bending and stretching constraints per atom, C av . C av is a linear function of N av :C av = 2.5N av - 3, with ideal, low defect density glasses and thin films having values of N av and C av equal to 2.4, and 3.0, respectively. In over-constrained films, it has been argued and demonstrated experimentally, that the density of intrinsic defects is proportional to N av - 2.4. In this paper we demonstrate that this scaling relationship, with the same empirical constants applies to floppy or under-constrained films with the example being a-Se where N av has been determined from EXAFS studies and is ∼2.2. In addition we demonstrate that the density of defects in as deposited a-Si with a 6% density deficit, and broken bonding constraints, can be treated in the same way as spacing-filling over-constrained networks.

Studies of amorphous (a-) semiconductors have been driven by technological advances as well as fundamental theories. Observation of electrical switching, for example, fueled early interest in a-chalcogenides. More recently a-chalcogenide switching has been applied successfully to programmable memory devices as well as DVD technology where the quest for the discovery of better-suited materials continues. Thus, switching grants researchers today with an active arena of technological as well as fundamental study. Bond constraint theory (BCT) and rigidity theory provide a powerful framework for understanding the structure and properties of a-materials. Application of these theories to switching in a-chalcogenides holds the promise of finding the best composition suited for switching applications. Extended X-ray absorption fine structure (EXAFS) spectroscopy is an ideally suited technique to investigate the switching properties of these materials. Films of amorphous Ge 2 Sb 2 Te 4 , Ge 2 Sb 2 Te 5 , and Ge 2 Sb 2 Te 7 exhibit differing bonding structures and bond statistics, which result in different electronic and optical properties. Results of new EXAFS experiments on these three critical compositions in the Ge–Sb–Te system are presented in light of BCT and rigidity theory.

Ge 2 Sb 2 Te 5 is one of the chalcogenide alloy materials of choice for ReWritable (RW) optical discs that are currently in manufacturing; however, there are many issues relating to the physics and chemistry underpinning the switching mechanism that have as yet to be resolved. This is paper identifies important relationships between the chemical bonding in the non-crystalline phase of Ge 2 Sb 2 Te 5 , and in the face-centered-cubic (FCC) nano-crystalline alloy phase that account for the markedly different optical and electrical properties that are enabling for memory applications. The non-crystalline material is characterized as an intermediate phase (IP) with minimal (i) bond-strain and (ii) extended macroscopic-strain, and includes a precursor bonding arrangement crucial to optical and electronic RW memories. The FCC phase has nano-crystallites trapped in a metastable diphasic composite that is stabilized by the inclusion of non-crystalline GeTe x ( x ∼ 5) nano-clusters pinned at grain boundaries.

We have performed an experimental study of the effects of ionizing radiation and bias-temperature stress on Si MOS devices with HfSiON gate dielectrics. We compare the responses of homogeneous high-SiN films and low-SiN films that contain crystalline HfO. We observe that the low-SiN films are more sensitive to ionizing radiation than the high-SiN films. In particular, the low-SiN film that includes crystalline HfO is especially vulnerable to electron trapping due to substrate injection under positive irradiation bias. Both film types exhibit reduced radiation-induced charge trapping relative to previous Hf silicates. The high-SiN film exhibits less radiation-induced net oxide-trap charge density than earlier Hf silicate films processed without nitride. We also find that these devices are relatively robust against bias-temperature stress instabilities. Consistent with the radiation response, the low-SiN devices also display elevated levels of charge trapping relative to the high-SiN devices during bias-temperature stress.

This paper identifies different length scales λs for strain-reducing chemical bonding self-organizations (CBSO) in non-crystalline and nano-crystalline thin films. CBSOs are differentiated spectroscopically, and explained by semi-empirical bond-constraint theory (SE-BCT). Non-crystalline thin film CBSOs are characterized by molecular scale, strain-reducing chemical ordering with λs > 0.6 nm, and extending to at most 1 nm. The non-random bonding results in reduced defect densities that are enabling for device applications. Nano-crystalline transition metal oxide thin films display qualitatively different properties in two distinct nano-scale regimes in which the length scale metric is defined by π-bond coupling between atoms in strings of neighboring primitive unit cells (PUCs): (i) type I with nano-grain dimensions and λs ∼ 2 nm (or 3–4 nm (>6 PUCs). There are also diphasic nano-crystalline/non-crystalline technologically important thin films in which strain percolation is also minimized by CBSOs that combine molecular and PUC scales of order. Representative non-crystalline, nano-crystalline and diphasic nano-crystalline/non-crystalline thin film materials with qualitatively different behaviors and degrees of phase stability/metastability are addressed.

Ab initio quantum mechanical calculations have been performed on cluster models of Zr/ZrO2 and Hf/HfO2 interfaces. The theoretical method is a first principles method in which an exact electrostatic Hamiltonian is employed, except for core electron effective potentials, and wavefunctions are constructed by a self-consistent-field (SCF) method in which ionic correlation is included by local configuration interaction (CI). The outcome of the calculations is a detailed prediction of the electronic structure of the interface from which electrical properties can be inferred; e.g., work function, surface dipoles, barriers to electron transport, etc.. The results are compared with and also serve to calibrate electronegativity arguments that lead to predictions of surface dipole changes when Zr or Hf metals are deposited on the respective elemental oxides. In the present work the cluster describing the Zr/ZrO2 interface was embedded in an electrostatic field that simulates more distant Madelung contributions, and removes unphysical solutions as well.

Ab initio quantum mechanical calculations have been performed on cluster models of Zr/ZrO"2 and Hf/HfO"2 interfaces. These calculations give detailed predictions of the electronic structure of the interface from which electrical properties can be inferred; e.g., work function, surface dipoles, barriers to electron transport, etc.. The results are compared with and also serve to calibrate electronegativity arguments that lead to predictions of surface dipole changes when Zr or Hf metals are deposited on the respective elemental oxides. In the present work the cluster describing the Zr/ZrO"2 interface was embedded in an electrostatic field that simulates more distant Madelung contributions, and removes unphysical solutions as well.

This paper applies near edge X-ray absorption spectroscopy (NEXAS) and soft-X-ray photoelectron spectroscopy (SXPS) to identity different length scales of nano-crystallinity in transition metal (TM) elemental oxides. Jahn-Teller (J-T) splittings in band edge HfO2 Eg states in O K1 NEXAS spectra requires nano-crystalline grain-sizes >3 to 4 nm and coherent p-bonding interactions. The spectroscopic studies provide an unambiguous way to distinguish between two regimes of nano-crystalline order with coherent and incoherent p-bonding interactions, yielding significant information on band edge electronic structure, and electronically active defects as well. Finally, defects in non-crystalline Hf Si oxynitride alloys are shown to be qualitatively different than those in either the nano-crystalline scale regimes.

Thin films with intermediate phase (IP) bonding regimes have been incorporated into optical, electrical and other devices, and semiconductor dielectric interfaces as well. These IPs result from chemical bonding self-organizations that suppress local bond-strain, are associated with chemically-ordered-rather than random-alloy-bonding, and in many instances break bond-bending constraints through local site symmetry reductions.