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There has been tremendous research effort in hunting for novel two-dimensional (2D) materials with exotic properties, showing great promise for various potential applications. Here, we report the findings about a new hexagonal phase of 2D Ga2O3 and In2O3, with high energetic stability, using a global searching method based on an evolutionary algorithm, combined with density functional theory calculations. Their structural and thermal stabilities are investigated by the calculations of their phonon spectra and by ab initio molecular dynamics simulations. They are predicted to be intrinsically non-magnetic stable semiconductors, with a flatband edge around the valence band top, leading to itinerant ferromagnetism and half-metallicity upon hole doping. Bilayer Ga2O3 is also studied and found to exhibit ferromagnetism without extra hole doping. The Curie temperature of these materials, estimated using Monte Carlo simulations based on the Heisenberg model, is around 40–60 K upon a moderate hole doping density.

Spectral analysis of optically excited currents in single-crystal (100)InAs/amorphous (a-)Al2O3/ metal structures allows one to separate contributions stemming from the internal photoemission (IPE) of electrons into alumina and from the trapping-related displacement currents. IPE spectra suggest that the out-diffusion of In and, possibly, its incorporation in a-Al2O3 lead to the development of 0.4 eV wide conduction band (CB) tail states. The top of the InAs valence band is found at 3.4560.10 eV below the alumina CB bottom, i.e., at the same energy as at the GaAs/a-Al2O3 interface. This corresponds to the CB and the valence band offsets at the InAs/a-Al2O3 interface of 3.160.1 eV and 2.560.1 eV, respectively. However, atomic-layer deposition of alumina on InAs results in additional low-energy electron transitions with spectral thresholds in the range of 2.0–2.2 eV, which is close to the bandgap of AlAs. The latter suggests the interaction of As with Al, leading to an interlayer containing Al-As bonds providing a lower barrier for electron injection. received: 2016-09-05 accepted: 2016-11-17 published: 2016-12-15 ispartof: Journal of Applied Physics vol:120 issue:23 pages:235701-1 status: published

Hole-doped monolayer SnO has been recently predicted to be a ferromagnetic material, for a hole density typically above 5x1013/cm2. The possibility to induce a hole-doped stable ferromagnetic order in this two-dimensional material, either by intrinsic or extrinsic defects, is theoretically studied, using first-principles simulations. Sn vacancies and Sn vacancy-hydrogen complexes are predicted to be shallow acceptors, with relatively low formation energies in SnO monolayers grown under O-rich conditions. These defects produce spin-polarized gap states near the valence band-edge, potentially stabilizing the ferromagnetic order in 2D SnO. Hole-doping resulting from substitutional doping is also investigated. Among the considered possible dopants, As, substituting O, is predicted to produce shallow spin-polarized gap states near the valence band edge, also potentially resulting in a stable ferromagnetic order in SnO monolayers.

The electron energy band alignment in the Si/HfxTi1−xO2/metal (Au,Al) structures is determined as a function of oxide composition using internal photoemission of electrons and photoconductivity measurements. For x⩽0.5 the electron excitations with thresholds corresponding to the band-gap width of amorphous TiO2 (4.4 eV) and HfO2 (5.6 and 5.9 eV) are observed at the same time, suggesting formation of TiO2- and HfO2-like subnetworks. With respect to the Fermi level of Au the conduction band of TiO2 appears to be 1.4 eV below the conduction band of HfO2 which indicates that the valence bands of the two oxides are nearly aligned. This significant downshift of the conduction band due to Ti incorporation leads to low barriers for electrons at the interfaces of HfxTi1−xO2 with Si and Al (∼1 eV or less) strongly impairing insulating properties of the oxide. Crystallization of TiO2 upon high-temperature annealing further enhances leakage currents because of a significantly lower band-gap width of crystallized TiO2...

Charge trapping in high-permittivity metal oxides (Al2O3, ZrO2, and HfO2) grown on (100)Si using various types of chemical vapor deposition (CVD) was studied using generation of electron-hole pairs in the oxide by 10 eV photons. For most of the CVD methods, thin (≈5 nm) oxide films exhibit positive charging suggesting hole trapping as most efficient charge trapping process. Negative charge is observed only in as-deposited nitrogen-containing films grown from Hf(NO3)4. The trapped positive charge depends only weakly on the HfO2 thickness indicating that holes are trapped in a silicon oxide interlayer grown between the Si and HfO2 during deposition, which is further affirmed by enhanced positive charging after additional oxidation of the samples at high temperatures. The work function of the metal electrode material has a large influence on hole trapping in thin oxides, indicating electron exchange between the metal and defect states in the oxide. In addition, trapping of positive charge correlates with lib...

The energy barrier height Φ for electrons at the interfaces of various metals (Mg,Al,Ni,Cu,Au) with nanometer-thin Al2O3 and ZrO2 layers grown on (100)Si by atomic layer deposition has been directly measured using internal photoemission of electrons into the insulator. The behavior of the metal/Al2O3 contacts with increasing metal electronegativity XM resembles that of the metal/SiO2 interfaces with ideality factor dΦ/dXM≈1. The metal/ZrO2 contacts exhibit a less ideal behavior with dΦ/dXM≈0.75. The metal–silicon work function differences in structures with Al2O3 and ZrO2 insulators appear to be considerably larger than in the structures with thermally grown SiO2, suggesting the presence of a negative dipole layer at the metal/deposited oxide interface.

In this work, we studied low-field leakage currents in the self-assembly based spin-on low-k dielectrics (k = 2.2) as it may be affected by the degree of the organic template decomposition. The distinct role of the template residues could be examined due to the remarkably different rate of organosilica matrix cross-linking and template decomposition during the hard-bake process. We found that the incomplete decomposition of the sacrificial organic phase is responsible for increased low-field leakage current through the dielectric. The analysis of photocurrent spectra and the results of electron resonance spectroscopy suggest that the degradation of electrical performance can be attributed to the presence of defect states ∼5 eV below the insulator conduction band induced by the residues in the form of oxidized sp3-carbon chains. The lowest leakage current is attained in the template-free material obtained by introduction of additional broadband UV-assisted curing (λ > 200 nm).

The simultaneous action of passivation and dissociation during thermochemical interaction of trivalent interfacial Si traps (Pb’s;Si3≡Si⋅) with molecular hydrogen has been analyzed. A unified description is attained through solution of the simultaneous set of the first-order rate equations describing passivation and dissociation, under the restriction that the H2 concentrations at the interface and in the ambient are continuously equal. The analysis is given allowance by the recently attained physically consistent pictures for each of the separate steps of passivation in H2 and dissociation in vacuum, incorporating the existence of distinct spreads σEf and σEd in the respective activation energies. The assessment of heat treatment in H2 shows that, as compared to the fictitious case σEf=σEd=0, the effect of the existence of the spreads, for usual anneal times of 10–60 min in 1 atm H2, is to reduce the passivation efficiency by two orders of magnitude, while enhancing the optimum anneal temperature Tan fro...

The electrical characteristics of SiOx/ZrO2 and SiOx/Ta2O5 gate dielectric stacks are investigated. The current–density JG in these dielectric stacks is shown to be strongly temperature dependent at low voltage (below about 2 V), the more so in the ZrO2 stack. On the other hand, JG is much less temperature dependent at higher voltage. These results are consistent with a model which takes into account the direct tunneling of electrons across the SiOx layer and the trap-assisted tunneling of electrons through traps with energy levels below the conduction band of the high permittivity dielectric layer. The energy levels and densities of these electron trapping centers are estimated by fitting this trap-assisted tunneling model to the experimental results.

The suppression of thermally induced generation of hole traps in SiO2 layers of Si/SiO2 and poly-Si/SiO2/Si structures by He ambient is analyzed as a function of the gas pressure p. The pressure dependence of the suppression efficiency is found close to p2/3. This pressure dependence and the observed reduced suppression efficiency of heavier noble gases (Ne, Ar) are interpreted as indications that the gas atom dissolved in SiO2 should approach close to the degradation-prone site in order to prevent the thermally induced bond break. This result suggests that a short-range interaction between noble gas atoms and the Si/SiO2 network atoms is at the basis of the degradation blockage effect.

Spectroscopic ellipsometry was used to determine the density of oxides thermally grown on Si substrates as a function of the oxidation temperature, and the time and temperature of postoxidation anneals. All the oxides were found to be denser than fused silica. The density of the as-grown oxides was found to decrease as the growth temperature was increased. Postoxidation anneals were found to reduce the oxide density; high temperature or long-time anneals caused the greatest reduction in density. Holes alone, or holes and electrons, were injected into the oxides by irradiating with vacuum ultraviolet light or x rays under electric field bias. Using capacitance–voltage measurements, it was found that low-density oxides trap charge more efficiently than high-density oxides. Electron spin resonance measurements indicated that, for most of these oxides, the number of paramagnetic defects was substantially smaller than the number of trapped charges. It is hypothesized that the additional, nonparamagnetic, charge is in the form of protons trapped near network oxygen atoms that have large Si–O–Si bond angles. The number of these large-angle bonds in the near-interfacial oxide increases as the oxide density decreases, explaining the observed correlation between the charge trapping and the oxide density.

Electron spin resonance (ESR) on thermal (100)Si/SiO2 predominantly exhibiting either the Pb0 or Pb1 interface defect confirms the Pb1 point symmetry as monoclinic-I with g1=2.0058, g2=2.00 735±0.00 010, and g3=2.0022, where the g2 direction is at 3°±1° (towards the interface) with a 〈111〉 direction at 35.3° with the interface plane. Its line width is found weakly dependent on magnet angle, exhibiting a strain induced spread σg⊥∼0.00 035 in g⊥ about 2–3 times less than typical for Pb in (111)Si/SiO2. For Pb0, an axially symmetric g matrix is observed, with g∥=2.0018 and g⊥=2.0081, and σg⊥∼0.0009. From comparison of salient ESR data, it is concluded that Pb and Pb0 are chemically identical; however, systematic fabrication-induced variations in defect environment will lead to second order systematic shifts in average properties. The Pb1 defect is provisionally pictured as an unpaired Si bond on a defect Si atom at slightly subinterface plane position in the Si substrate, possibly facing an oxygen atom.

The microstructure and electrical properties of buried SiO2 layers produced in silicon by the implantation of oxygen ions are analyzed in terms of implantation parameters and supplemental incorporation of oxygen. The buried oxides show inhomogeneous etching in aqueous HF, revealing the presence of a crystalline oxide phase and Si-enriched regions. Silicon enrichment in SiO2 is found in the form of Si inclusions and oxygen deficient network defects. The former are found to be sensitive to the oxygen implantation profile, and may arise as a result of a blockage of Si outdiffusion by crystalline oxide inclusions. The network defects, in turn, are predominantly generated during high temperature postimplantation annealing, caused possibly by some mechanism of silicon transport from the interfaces into the bulk of oxide. The electron trapping and electrical conduction characteristics of buried oxides are found to correlate with the density and size of the inhomogeneities. By contrast, hole trapping and the gene...

The electron energy band alignment between (100)Si and several complex transition/rare earth (RE) metal oxides (LaScO3, GdScO3, DyScO3, and LaAlO3, all in amorphous form) is determined using a combination of internal photoemission and photoconductivity measurements. The band gap width is nearly the same in all the oxides (5.6-5.7 eV) yielding the conduction and valence band offsets at the Si/oxide interface of 2.0+/-0.1 and 2.5+/-0.1 eV, respectively. However, band-tail states are observed and these are associated with Jahn-Teller relaxation of transition metal and RE cations which splits their d* states. (C) 2004 American Institute of Physics.

Electron spin resonance (ESR) measurements on (100)Si∕SiOx∕ZrO2 and (100)Si∕Al2O3∕ZrO2 stacks with nm-thick dielectric layers reveal, upon postdeposition oxidation (PDO) in the range of 650–800°C, the appearance of various SiO2-characteristic defects, including E′ and EX centers and a 95‐G doublet. These defects generally grow during PDO treatment, attesting to significant modification of the SiOx interlayer, and∕or additional SiOx interlayer growth. The ESR results on E′ indicate that the SiOx interlayer formed in (100)Si∕SiOx∕ZrO2 is drastically inferior to standard thermal (100)Si∕SiO2, exhibiting over one order of magnitude more O-deficiency centers. The (100)Si∕Al2O3 system appears more robust in terms of SiOx interlayer growth, and has better interlayer properties.

Electron energy band alignment in GaAs(100)∕Ga2O3∕GdxGa0.4−xO0.6 structures was determined using internal photoemission and photoconductivity measurements. Two band gap values associated with Ga2O3(4.8eV) and Gd2O3(5.8eV) subnetworks were revealed. They yield potential barriers between the GaAs valence band and the bottom of the Ga2O3 and Gd2O3 derived conduction bands of 2.2 and 2.9eV, respectively. The corresponding conduction band offsets at the GaAs∕oxide interface, 0.8 and 1.5eV, indicate the possibility of significant reduction of electron injection in Gd-rich oxides.

The energy distributions of interface states were determined in (100)Si/HfO2 using capacitance–voltage measurements on structures with the periphery of the metal electrode switched to inversion by controlled application of corona discharge. Together with independently applied ac conductance spectroscopy they reveal a strong impact of the HfO2 deposition technique on the interface trap density. This includes the enhancement of the Si-dangling bond defect (Pb0 centers) density and a contribution of insulator-related traps in samples deposited using a nitrogen-containing precursor.

Electron spin resonance (ESR) analysis reveals the incorporation of N in (100)Si/HfO2 structures with ultrathin amorphous HfO2 films deposited by chemical vapor deposition (CVD) using Hf(NO3)4 as precursor, through detection, after 60Co γ-irradiation, of NO2 radicals (density ≳55 at. ppm). The molecules are found to be stabilized and likely homogeneously distributed in the HfO2 network. Some network forming N entity is suggested as a precursor, transformed into ESR-active NO2 upon γ-irradiation. The interesting N incorporation aspect appears inherent to the particular CVD process.

The Ge/HfO2 interface band diagram was directly determined using internal photoemission of electrons and holes from Ge into the Hf oxide. The inferred offsets of the conduction and valence band at the interface, 2.0±0.1 and 3.0±0.1 eV, respectively, suggest the possibility to apply the deposited HfO2 as an insulator on Ge. The post-deposition annealing of the Ge/HfO2 structures in oxygen results in ∼1 eV reduction of the valence band offset attributed to the growth of GeO2 interlayer.

The generation of point defects in Si/SiO2/Al capacitors due to exposure to vacuum ultraviolet (VUV) (10 eV) radiation has been investigated by studying the electron and hole trapping properties and electron‐spin‐resonance spectroscopy for exposures ranging from 1014 up to 1019 photons cm−2 absorbed in the oxide. At low VUV exposures, the generation of hydroxyl groups and electron traps with cross section ≥10−16 cm2 is observed; however, for exposures larger than 1017 cm−2 these centers are subsequently eliminated. For exposures larger than 1018 cm−2 the oxide network is gradually destroyed; oxygen atoms are removed from their network positions and decorated with hydrogen atoms, thus producing water molecules and trivalent silicon centers in comparable numbers. At an exposure of 1019 cm−2, of the order of 1014 cm−2 of oxygen atoms are removed, without any indication that the process would saturate. A tentative model is presented in which the degeneration process takes place at regular network sites; a defect precursor is not invoked. It is proposed that neutralization of self‐trapped hydrogen/hole pairs at the oxygen atoms plays a crucial role in this process.

Low-temperature (T = 1.7-77 K) multi frequency electron spin resonance (ESR) study on p-type 2H-polytype geological MoS2 crystals reveals p-type doping predominantly originating from As atoms substituting for S sites in densities of (2.4 +/- 0.2) x 10(17) cm(-3). Observation of a "half field" (g similar to 3.88) signal firmly correlating with the central Zeeman As accepter signal indicates the presence of spin S > 1/2 As agglomerates, which together with the distinct multicomponent makeup of the Zeeman signal points to manifest non-uniform As doping; only similar to 13% of the total As response originates from individual decoupled As dopants. From ESR monitoring the latter vs. T, an activation energy E-a = (0.7 +/- 0.2) meV is obtained. This unveils As as a noticeable shallow acceptor dopant, appropriate for realization of effective p-type doping in targeted 2D MoS2-based switching devices. ispartof: Applied Physics Letters vol:109 issue:17 status: published

Analysis of photodepopulation of electron traps in HfO2 films grown by atomic layer deposition is shown to provide the trap energy distribution across the entire oxide bandgap. The presence is revealed of two kinds of deep electron traps energetically distributed at around Et ≈ 2.0 eV and Et ≈ 3.0 eV below the oxide conduction band. Comparison of the trapped electron energy distributions in HfO2 layers prepared using different precursors or subjected to thermal treatment suggests that these centers are intrinsic in origin. However, the common assumption that these would implicate O vacancies cannot explain the charging behavior of HfO2, suggesting that alternative defect models should be considered.

A novel charge sensing technique, based on monitoring donor defects in near‐interfacial Si by electron spin resonance (ESR), has been applied to measure positive charge in buried oxide (BOX) layers of separation by implantation of oxygen material. This positive charge is introduced into the BOX layer by annealing in hydrogen in the temperature range 450–700 °C. Standard capacitance‐voltage (C‐V) analysis of the areal BOX‐charge densities was used as a crucial test for this ESR‐based method, yielding good agreement between the two techniques. Photoinjection of charges, optical excitation, and C‐V and ESR etchback experiments have been performed on BOX layers subsequent to the hydrogen charging treatment leading to additional information on location, nature, and stability of the hydrogen‐induced positive centers. The results show that these centers are very stable (not even affected by electron injection) and that they are located near the two Si/BOX interfaces (within a layer of ≤20 nm).

Electron spin resonance analysis of (100)Si/HfO2 interfaces prepared by chemical vapor deposition of the oxide using three chemically different precursors reveals that the trivalent Si defects common for Si/SiO2 interfaces—Pb0 and Pb1 centers—are universally observed upon hydrogen detachment. The density of the Pb0 is higher than in the (100)Si/SiO2 structures and is sensitive to the deposition process. However, the density can be significantly reduced by annealing of the Si/HfO2 structures in O-containing ambient, likely through re-establishing the Si/SiO2 interface. Also, the Pb-type centers can be entirely passivated by hydrogen already at 400 °C. The density of fast interface states closely follows the variations in the Pb0 center density, suggesting it as the dominant contribution to the fast interface states.

The results of a series of experiments are reported in which constant, controlled levels of in-plane stress were applied in situ to oxidizing (111) silicon substrates. Electron spin resonance measurements show that the properties of inherently incorporated electrically active Pb defects at the (111)Si/SiO2 interface are affected; among others, tensile stresses decrease the number of Pbs, while compressive stresses have the opposite effect. The results are in agreement with the generally accepted relationship between Pb-defect generation and interfacial mismatch (stress).

Electron spin resonance (ESR) analysis reveals that the versatile noncontacting corona biasing method frequently applied in the electrical analysis of Si/SiO2-based structures is not a noninvasive tool, as usually assumed. In the absence of carrier impact damage, at least five types of ESR-active defects are generated, indicating the drastic impact and jeopardizing inference of intrinsic device properties.

Si dangling bond interface defects (Pb0,Pb1) were probed by electron spin resonance in entities of (100)Si with ultrathin SiO2 grown in ozonated de-ionized water solution at room temperature. After photodesorption of passivating hydrogen, Pb0 appears with densities up to ∼5×1012 cm−2, a value five times larger than the one standardly attained with high temperature thermal growth. Thus standard quality thermal Si/SiO2 interface properties, as exposed by the Pb0-type defects criterion (interface traps), are not obtained by oxidation in ozonated water solutions at room temperature. The interface quality may be upgraded by providing additional thermal budget. Yet standard qualitity is still not attained after vacuum annealing at 600 °C.

Depositing HfO2 layers on ultrathin thermally grown SiO2 on 4H–SiC(0001) is demonstrated to yield an insulator with good properties. The stack combines the high quality of the ultrathin SiO2/SiC interface and associated high energy barriers for electron and hole injection from SiC with the high dielectric permittivity of HfO2 (≈20). The latter allows application of high electric fields to the SiC surface (up to 3 MV/cm), while keeping the strength of the field in the insulator at a moderate level.

An analysis of fast and slow traps at the interface of 4H–SiC with oxides grown in O2, N2O, and NO reveals that the dominant positive effect of nitridation is due to a significant reduction of the slow electron trap density. These traps are likely to be related to defects located in the near-interfacial oxide layer. In addition, the analysis confirms that the fast interface states related to clustered carbon are also reduced by nitridation.

Internal electron photoemission is used to investigate the electronic structure of the Si/Hf–Al oxide interfaces as a function of oxide composition. In the mixed oxides, the energy position and the density of states in the conduction band show little sensitivity to the Hf content. At the same time, the energy band diagram of the Si/oxide interface appears to be very close to that of the Si/Al2O3 interface, suggesting that the conduction band is derived mostly from the states of Al ions.

The generation of delocalized E’δ defects through hole injection in buried SiO2 (BOX) layers of standard separation‐by‐implantation‐of‐oxygen structures has been studied by electron spin resonance. Selective photoinjection of holes was carried out under positive biasing of deposited semitransparent electrodes. This leads to the production of numerous delocalized E’δ centers (density≊1.8×1013 cm−2) in addition to a large density (∼9×1013 cm−2) of the common E’γ defect (O3≡Si⋅+Si≡O3)—a result qualitatively similar to previous glow discharge damage data. Comparison of damaging agents applied to BOX indicates that E’γ and E’δ defects are generally produced in an approximately fixed relative ratio. The comparison further bears out that, while energetic photons (x and γ) and ion bombardment activate similar E’δ defects of axial symmetry, hole injection generates a more isotropic type, termed E’δ2. It reveals the tendency that as the damaging species gets ‘‘softer,’’ the g matrix anisotropy fades together with t...

A K‐band electron‐spin‐resonance study of the appearance of the delocalized intrinsic EX center in dry thermal SiO2 was performed on (001) and (111) Si/SiO2. The defect is found in both structures in nearly identical spin densities, 1.2×1012 cm−2 being the maximum areal density. Variation of Si precleaning treatments showed the center’s generation to depend on the initial surface condition of the c‐Si substrate. For fixed initial surface conditions, however, systematic variation of the oxidation temperature (760–930 °C), oxidation time (a few min up to 24 h), and oxygen pressure (∼24 and ∼110 kPa), in combination with stylus profilometry, revealed the EX areal density to be solely determined by the grown oxide thickness (dox), EX being detectable from dox≊70 A onwards, with a maximum intensity at dox≊125 A. Etch back experiments showed the defects to reside in the top 45 A of the oxide layer, with the largest local volume density (∼3×1018 cm−3) occurring near the ambient/SiO2 interface. With growing oxide...

Atomic-layer-deposited layers of Al2O3 on (100)Si are shown to transform into γ-Al2O3 when treated at temperatures above 800 °C. The compaction process leads to widening of the alumina band gap and causes an ≈0.5 eV upward shift of the oxide conduction band with respect to the Fermi level of Au and Al. In the case of incomplete transformation of the Al2O3 film, large leakage currents across the oxide are observed, which are explained by the formation of conducting grain boundaries similar to those formed on γ-alumina surfaces.

The electron energy band alignment at the Si/HfO2 interfaces with different interlayers (Si3N4, SiON, and SiO2) is directly determined using internal photoemission of electrons and holes from Si into the Hf oxide. Irrespective of the interlayer type, the energy barrier for the Si valence electrons was found to be equal 3.1±0.1 eV, yielding the conduction band offset of 2.0±0.1 eV. Photoemission of holes is effectively suppressed by SiON and SiO2 interlayers, yet it is observed to occur across the Si3N4 interlayer with a barrier of 3.6±0.1 eV, which corresponds to a Si/HfO2 valence band offset of 2.5±0.1 eV. The HfO2 band gap width of 5.6 eV, thus derived from the band offsets, coincides with the bulk value obtained from the oxide photoconductivity spectra.

The structural degradation of thermal SiO2 on (100)Si under isochronal vacuum annealing in the range Tan=950 °C–1250 °C was monitored by electron spin resonance (ESR) in terms of point defect creation, including Eγ′, Eδ′, EX and the elusive predominant degradation-center S. Depth profiling after heating at 1200 °C shows that the S centers predominantly reside near the oxide borders, generally in anticorrelation with the Eγ′ distribution. The resulting anisotropic demagnetization effect has enabled inference of the S center susceptibility. As to the nature of the S center, an observed weak hyperfine structure may comply with the S center being of the type SinO3−n≡Si⋅ either the single n=1 or a mix of both the n=1,2 variants.

Electron spin resonance on (100)Si/SiOx/ZrO2 and (100)Si/Al2O3/ZrO2 stacks with nm-thin dielectric layers reveals the Si dangling-bond-type centers Pb0, Pb1 as prominent defects at the (100)Si/dielectric interface. This Pb0, Pb1 fingerprint indicates that, while gratifying for the Si/SiOx/ZrO2 case, the as-deposited (100)Si/Al2O3 interface is basically Si/SiO2-like. The interfaces are in an enhanced (unrelaxed) stress state, characteristic of low-temperature Si/SiO2 growth. Based on the Pb0, Pb1 criterion, standard thermal Si/SiO2 interface properties may be approached by appropriate annealing (⩾ 650 °C) in vacuum in the case of Si/SiOx/ZrO2. Yet, O2 ambient is required for Si/Al2O3, indicating that the initial abruptness of the interface prevents thermal adaptation to occur until an additional SiOx interlayer grows. A minimal SiOx interlayer thickness (≳0.5 nm) appears requisite.

Optical injection of electron-hole pairs in 3–5 nm thick layers of SiO2, Al2O3, ZrO2 and their stacks on (100)Si is found to result in positive oxide charging, suggesting trapping of holes. In thin layers of the high-permittivity metal oxides (Al2O3, ZrO2), the positive charge exhibits a remarkable stability to neutralization by electrons which is neither observed in thicker layers of the same oxides nor in thermal SiO2. Most of the positive charge is associated with diamagnetic centers (possibly, protons).

Point defects induced at the exit surface of optical-grade fused silica by high power (>30 J/cm2) 355 nm laser pulses have been investigated to elucidate the nature of laser damage in optics for use at high peak powers (>2 GW/cm2). Six defects have been identified. Eγ′ and E74′ defects were identified using electron spin resonance spectroscopy. The nonbridging oxygen hole center, a self-trapped exciton, an oxygen-deficient center, and interstitial O2 were identified and spatially resolved in the damage craters using cathodoluminescence microanalysis. The defects are associated with the laser generated shock waves and/or thermal explosion.