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Silicene, the silicon counterpart of graphene, has been successfully grown on metallic substrates such as Ag(111), ZrB2(0001), and Ir(111) surfaces. However, characterization of its electronic structure is hampered by the metallic substrate. In addition, potential applications of silicene in nanoelectronic devices will require its growth on or integration with semiconducting and insulating substrates. We herein present a review of recent theoretical works regarding the interaction of silicene with non-metallic templates, distinguishing between the weak van-der-Waals-like interactions of silicene with, for example, layered metal (di)chalcogenides, and the stronger covalent bonding between silicene and, for example, ZnS surfaces. We then present a methodology to effectively compare the stability of diverse silicene structures using thermodynamics and molecular dynamics density functional theory calculations. Recent experimental results on the growth of silicene on MoS2are also reported and compared to the theoretical predictions.[Figure not available: see fulltext.]

Al₂O₃ on Si is known to form an ultra-thin interfacial SiO₂ during deposition and subsequent annealing, which creates a negative fixed charge (Qfᵢₓ) that enables field-effect passivation and low surface recombination velocities in Si solar cells. Various concepts were suggested to explain the origin of this negative Qfᵢₓ. In this study we investigate Al–O monolayers (MLs) from atomic layer deposition (ALD) sandwiched between deliberately grown/deposited SiO₂ films. We show that the Al-atoms have an ultra-low diffusion coefficient (~4×10⁻¹⁸ cm²/s at 1000°C), are deposited at a constant rate of ~5×10¹⁴ Al-atoms/cm²/cycle from the first ALD-cycle on, and are tetrahedral O-coordinated, since the adjacent SiO₂ imprints its tetrahedral near-order and bond length into the Al–O MLs. By variation of the tunnel-SiO₂ thickness and the number of Al–O MLs, we demonstrate that the tetrahedral coordination alone is not sufficient for the formation of Qfᵢₓ but that a SiO₂ /Al₂O₃ interface within a tunneling distance from the substrate must be present. The Al-induced acceptor states at these interfaces have energy levels slightly below the Si valence band edge and require charging by electrons from either the Si substrate or from Si/SiO₂ dangling bonds to create the negative Qfᵢₓ. Hence, tunneling imposes limitations for the SiO₂ and Al₂O₃ layer thicknesses. In addition, Coulomb repulsion between the charged acceptor states results in an optimum number of Al–O MLs, i.e., separation of both interfaces. We achieve maximum negative Qfᵢₓ of ~5×10¹² cm⁻² (comparable to thick ALD-Al₂O₃ on Si) with ~1.7 nm tunnel-SiO₂ and just 7 ALD-Al₂O₃ cycles (~8 Å) after optimized annealing at 850°C for 30 s. The findings are discussed in the context of a passivating, hole-selective tunnel contact for high-efficiency Si solar cells.

Silicene, the silicon counterpart of graphene, has been successfully grown on metallic substrates such as Ag(111), ZrB2(0001), and Ir(111) surfaces. However, characterization of its electronic structure is hampered by the metallic substrate. In addition, potential applications of silicene in nanoelectronic devices will require its growth on or integration with semiconducting and insulating substrates. We herein present a review of recent theoretical works regarding the interaction of silicene with non-metallic templates, distinguishing between the weak van-der-Waals-like interactions of silicene with, for example, layered metal (di)chalcogenides, and the stronger covalent bonding between silicene and, for example, ZnS surfaces. We then present a methodology to effectively compare the stability of diverse silicene structures using thermodynamics and molecular dynamics density functional theory calculations. Recent experimental results on the growth of silicene on MoS2are also reported and compared to the theoretical predictions.[Figure not available: see fulltext.]

Silicene has so far been successfully grown on metallic substrates, like Ag(111), ZrB2(0001) and Ir(111) surfaces. However, the characterization of its electronic structure is hampered by the metallic substrate. In addition, potential applications of silicene in nanoelectronic devices will require its growth/integration with semiconducting or insulating substrates. In this chapter, we review recent theoretical works about the interaction of silicene with several non-metallic templates, distinguishing between the weak van der Waals like interaction of silicene with e.g. AlN or layered metal (di)chalcogenides, and the stronger covalent bonding between silicene and e.g. ZnS surfaces. Recent experimental results on the possible growth of silicene on MoS2 are also highlighted and compared to the theoretical predictions.

By using first-principles simulations, we investigate the interaction of silicene and germanene with various non-metallic substrates. We first consider weak van der Waals interactions between the 2D layers and dichalcogenide substrates, like MoX2(X=S, Se, Te). The buckling of the silicene or germanene layer is correlated to the lattice mismatch between the 2D material and the MoX2template. The electronic properties of silicene or germanene on these different templates then largely depend on the buckling of the 2D material layer: highly buckled silicene or germanene on MoS2are predicted to be metallic, while low buckled silicene on MoTe2is predicted to be semi-metallic, with preserved Dirac cones at the K points. We next study the covalent bonding of silicene and germanene on (0001) ZnS and ZnSe surfaces. On these substrates, silicene or germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy band gap can be controlled by an out-of-plane electric field.

The electronic and vibrational properties of 2D honeycomb structures of molybdenum disulfide (MoS2) subjected to strain have been investigated using first-principles calculations based on density functional theory. We have studied the evolution of the electronic properties of bulk and layered MoS2, going down from a few layers up to a mono-layer, and next investigated the effect of bi-axial strain on their electronic structure and vibrational frequencies. Both for tensile and compressive bi-axial strains, the shrinking of the energy band-gap of MoS2with increasing level of applied strain is observed and a transition limit of the system from semiconducting to metallic is predicted to occur for strains in the range of 8-10%. We also found a progressive downshift (upshift) of both the E12gand A1gRaman active modes with increasing level of applied tensile (compressive) strain. Interestingly, significant changes in the curvature of the conduction and valence band near their extrema upon the application of strain are also predicted, with correlated variations of the electron and hole effective masses. These changes present interesting possibilities for engineering the electronic properties of 2D structures of MoS2. © 2012 Elsevier BV

Silicene and germanene are the silicon and germanium counterparts of graphene, respectively. Recent experimental works have reported the growth of silicene on (1 1 1)Ag surfaces with different atomic configurations, depending on the growth temperature and surface coverage. We first theoretically study the structural and electronic properties of silicene on (1 1 1) Ag surfaces, focusing on the (4 x 4) silicene/Ag structure. Due to symmetry breaking in the silicene layer (nonequivalent number of top and bottom Si atoms), the corrugated silicene layer, with the Ag substrate removed, is predicted to be semiconducting, with a computed energy bandgap of about 0.3 eV. However, the hybridization between the Si 3p orbitals and the Ag 5s orbital in the silicene/(1 1 1)Ag slab model leads to an overall metallic system, with a distribution of local electronic density of states, which is related to the slightly disordered structure of the silicene layer on the (1 1 1)Ag surface. We next study the interaction of silicene and germanene with different hexagonal non-metallic substrates, namely ZnS and ZnSe. On reconstructed (0 0 0 1)ZnS or ZnSe surfaces, which should be more energetically stable for very thin layers, silicene and germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy bandgap can be controlled by an out-of-plane electric field, an important finding for the potential use of these materials in nanoelectronic devices.

The interaction of germanene, the germanium counterpart of graphene, with (0001)ZnSe surfaces is investigated theoretically, using first-principles simulations. On a non-reconstructed (0001) ZnSe surface, germanene is predicted to be metallic, due to the pinning of the Fermi level by Se surface states. On a reconstructed (0001)ZnSe surface, which should be more energetically stable for very thin layers, the germanene layer is found to be semiconducting, with an energy band gap of about 0.4 eV. Remarkably, the nature (indirect or direct) and magnitude of this energy band gap can be controlled by an out-of-plane electric field, a semiconductor to metal transition being predicted for electric fields larger than about 0.6 V/Å. © The Electrochemical Society.

A first-principles modeling approach is used to investigate the vibrational properties of HfO2. The calculated phonon density of states is compared to experimental results obtained from inelastic electron tunneling spectroscopy (IETS) of various metal-oxide-semiconductor devices with HfO2gate stacks. This comparison provides deep insights into the nature of the signatures of the complicated IETS spectra and provides valuable structural information about the gate stack, such as the possible presence of oxygen vacancies in jet-vapour deposited HfO2. Important structural differences between the interface of atomic-layer or molecular-beam deposited HfO2and the Si substrate are also revealed. © 2011 American Institute of Physics.

By using first-principles simulations, we investigate the interaction of silicene and germanene with various non-metallic substrates. We first consider weak van der Waals interactions between the 2D layers and dichalcogenide substrates, like MoX2 (X=S, Se, Te). The buckling of the silicene or germanene layer is correlated to the lattice mismatch between the 2D material and the MoX2 template. The electronic properties of silicene or germanene on these different templates then largely depend on the buckling of the 2D material layer: highly buckled silicene or germanene on MoS2 are predicted to be metallic, while low buckled silicene on MoTe2 is predicted to be semi-metallic, with preserved Dirac cones at the K points. We next study the covalent bonding of silicene and germanene on (0001) ZnS and ZnSe surfaces. On these substrates, silicene or germanene are found to be semiconducting. Remarkably, the nature and magnitude of their energy band gap can be controlled by an out-of-plane electric field

We study the structural, mechanical and electronic properties of the twodimensional (2D) allotrope of tin: tinene/stanene using first-principles calculation within density functional theory, implemented in a set of computer codes. Continuing the trend of the group-IV 2D materials graphene, silicene and germanene; tinene is predicted to have a honeycomb lattice with lattice parameter of a0 = 4.62Å and a buckling of d0 = 0.92. The electronic dispersion shows a Dirac cone with zero gap at the Fermi energy and a Fermi velocity of ρF = 0.97 × 106 ms-1; including spin-orbit coupling yields a bandgap of 0.10 eV. The monolayer is thermally stable up to 700 K, as indicated by firstprinciples molecular dynamics, and has a phonon dispersion without imaginary frequencies. We explore applied electric field and applied strain as functionalization mechanisms. Combining these two mechanisms allows for an induced bandgap up to 0.21 eV, whilst retaining the linear dispersion, albeit with degraded electronic transport parameters

By using first-principles simulations, we investigate the interaction of a 2D silicon layer with two classes of chalcogenide-layered compounds, namely MoX2 and GaX (X = S, Se, Te). A rather weak (van der Waals) interaction between the silicene layers and the chalcogenide layers is predicted. We found that the buckling of the silicene layer is correlated to the lattice mismatch between the silicene layer and the MoX2 or GaX template. The electronic properties of silicene on these different templates largely depend on the buckling of the silicene layer: highly buckled silicene on MoS2 is predicted to be metallic, while low buckled silicene on GaS and GaSe is predicted to be semi-metallic, with preserved Dirac cones at the K points. These results indicate new routes for artificially engineering silicene nanosheets, providing tailored electronic properties of this 2D layer on non-metallic substrates. These non-metallic templates also open the way to the possible integration of silicene in future nanoelectronic devices

The structural and electronic properties of silicene and germanene on metallic and non-metallic substrates are investigated theoretically, using first-principles simulations. We first study the interaction of silicene with Ag(111) surfaces, focusing on the (4×4) silicene/Ag structure. Due to symmetry breaking in the silicene layer (nonequivalent number of top and bottom Si atoms), silicene is predicted to be semiconducting, with a computed energy gap of about 0.3 eV. However, the charge transfer occurring at the silicene/Ag(111) interface leads to an overall metallic system. We next investigate the interaction of silicene and germanene with hexagonal non-metallic substrates, namely ZnS and ZnSe. On reconstructed (semiconducting) (0001)ZnS or ZnSe surfaces, silicene and germanene are found to be semiconducting. Remarkably, the nature (indirect or direct) and magnitude of their energy band gap can be controlled by an out-of-plane electric field. © The Electrochemical Society

The interaction of silicene, the silicon counterpart of graphene, with (0001) ZnS surfaces is investigated theoretically, using first-principles simulations. The charge transfer occurring at the silicene/(0001) ZnS interface leads to the opening of an indirect energy band gap of about 0.7 eV in silicene. Remarkably, the nature (indirect or direct) and magnitude of the energy band gap of silicene can be controlled by an external electric field: the energy gap is predicted to become direct for electric fields larger than about 0.5 V Å-1, and the direct energy gap decreases approximately linearly with the applied electric field. The predicted electric field tunable energy band gap of the silicene/(0001) ZnS interface is very promising for its potential use in nanoelectronic devices. © the Owner Societies 2013

Internal photoemission measurements of barriers for electrons at interfaces between GaAs(111) and atomic-layer deposited Al2O3 indicate that changing the GaAs polar crystal face orientation from the Ga-terminated (111)A to the As-terminated (111)B has no effect on the barrier height and remains the same as at the non-polar GaAs(100)/Al2O3 interface. Moreover, the presence of native oxide on GaAs(111) or passivation of this surface with sulphur also have no measurable influence on the GaAs(111)/Al2O3 barrier. These results suggest that the orientation and composition-sensitive surface dipoles conventionally observed at GaAs surfaces are effectively compensated at GaAs/oxide interfaces. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698461]

From experiments on internal photoemission of electrons at the (100)InSb/Al2O3 interface, the top of the InSb valence band is found to be 3.05 +/- 0.10 eV below the oxide conduction band and corresponds to a conduction band offset of 2.9 +/- 0.1 eV. These results indicate that the top of valence band in InSb lies energetically at the same level as in GaSb and above the valence bands in InxGa1-xAs (0

Internal photoemission measurements of barriers for electrons at interfaces between GaAs(111) and atomic-layer deposited Al2O3 indicate that changing the GaAs polar crystal face orientation from the Ga-terminated (111)A to the As-terminated (111)B has no effect on the barrier height and remains the same as at the non-polar GaAs(100)/Al2O3 interface. Moreover, the presence of native oxide on GaAs(111) or passivation of this surface with sulphur also have no measurable influence on the GaAs(111)/Al2O3 barrier. These results suggest that the orientation and composition-sensitive surface dipoles conventionally observed at GaAs surfaces are effectively compensated at GaAs/oxide interfaces. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698461]

From experiments on internal photoemission of electrons at the (100)InSb/Al2O3 interface, the top of the InSb valence band is found to be 3.05 +/- 0.10 eV below the oxide conduction band and corresponds to a conduction band offset of 2.9 +/- 0.1 eV. These results indicate that the top of valence band in InSb lies energetically at the same level as in GaSb and above the valence bands in InxGa1-xAs (0

Monte Carlo (MC) methods have a long-standing history as partners of molecular dynamics (MD) to simulate the evolution of materials at the atomic scale. Among these techniques, the uniform-acceptance force-bias Monte Carlo (UFMC) method [ G. Dereli Mol. Simul. 8 351 (1992)] has recently attracted attention [ M. Timonova et al. Phys. Rev. B 81 144107 (2010)] thanks to its apparent capacity of being able to simulate physical processes in a reduced number of iterations compared to classical MD methods. The origin of this efficiency remains, however, unclear. In this work we derive a UFMC method starting from basic thermodynamic principles, which leads to an intuitive and unambiguous formalism. The approach includes a statistically relevant time step per Monte Carlo iteration, showing a significant speed-up compared to MD simulations. This time-stamped force-bias Monte Carlo (tfMC) formalism is tested on both simple one-dimensional and three-dimensional systems. Both test-cases give excellent results in agreement with analytical solutions and literature reports. The inclusion of a time scale, the simplicity of the method, and the enhancement of the time step compared to classical MD methods make this method very appealing for studying the dynamics of many-particle systems., Materials Science and Engineering, Mechanical, Maritime and Materials Engineering

Internal photoemission measurements of barriers for electrons at interfaces between GaAs(111) and atomic-layer deposited Al2O3 indicate that changing the GaAs polar crystal face orientation from the Ga-terminated (111)A to the As-terminated (111)B has no effect on the barrier height and remains the same as at the non-polar GaAs(100)/Al2O3 interface. Moreover, the presence of native oxide on GaAs(111) or passivation of this surface with sulphur also have no measurable influence on the GaAs(111)/Al2O3 barrier. These results suggest that the orientation and composition-sensitive surface dipoles conventionally observed at GaAs surfaces are effectively compensated at GaAs/oxide interfaces. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698461]

From experiments on internal photoemission of electrons at the (100)InSb/Al2O3 interface, the top of the InSb valence band is found to be 3.05 +/- 0.10 eV below the oxide conduction band and corresponds to a conduction band offset of 2.9 +/- 0.1 eV. These results indicate that the top of valence band in InSb lies energetically at the same level as in GaSb and above the valence bands in InxGa1-xAs (0

Monte Carlo (MC) methods have a long-standing history as partners of molecular dynamics (MD) to simulate the evolution of materials at the atomic scale. Among these techniques, the uniform-acceptance force-bias Monte Carlo (UFMC) method [ G. Dereli Mol. Simul. 8 351 (1992)] has recently attracted attention [ M. Timonova et al. Phys. Rev. B 81 144107 (2010)] thanks to its apparent capacity of being able to simulate physical processes in a reduced number of iterations compared to classical MD methods. The origin of this efficiency remains, however, unclear. In this work we derive a UFMC method starting from basic thermodynamic principles, which leads to an intuitive and unambiguous formalism. The approach includes a statistically relevant time step per Monte Carlo iteration, showing a significant speed-up compared to MD simulations. This time-stamped force-bias Monte Carlo (tfMC) formalism is tested on both simple one-dimensional and three-dimensional systems. Both test-cases give excellent results in agreement with analytical solutions and literature reports. The inclusion of a time scale, the simplicity of the method, and the enhancement of the time step compared to classical MD methods make this method very appealing for studying the dynamics of many-particle systems., Materials Science and Engineering, Mechanical, Maritime and Materials Engineering

The electronic properties of two-dimensional honeycomb structures of molybdenum disulfide (MoS2) subjected to biaxial strain have been investigated using first-principles calculations based on density functional theory. On applying compressive or tensile bi-axial strain on bi-layer and mono-layer MoS2, the electronic properties are predicted to change from semiconducting to metallic. These changes present very interesting possibilities for engineering the electronic properties of two-dimensional structures of MoS2. © 2012 Tsinghua University Press and Springer-Verlag Berlin Heidelberg

Internal photoemission measurements of barriers for electrons at interfaces between GaAs(111) and atomic-layer deposited Al2O3 indicate that changing the GaAs polar crystal face orientation from the Ga-terminated (111)A to the As-terminated (111)B has no effect on the barrier height and remains the same as at the non-polar GaAs(100)/Al2O3 interface. Moreover, the presence of native oxide on GaAs(111) or passivation of this surface with sulphur also have no measurable influence on the GaAs(111)/Al2O3 barrier. These results suggest that the orientation and composition-sensitive surface dipoles conventionally observed at GaAs surfaces are effectively compensated at GaAs/oxide interfaces. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3698461]

From experiments on internal photoemission of electrons at the (100)InSb/Al2O3 interface, the top of the InSb valence band is found to be 3.05 +/- 0.10 eV below the oxide conduction band and corresponds to a conduction band offset of 2.9 +/- 0.1 eV. These results indicate that the top of valence band in InSb lies energetically at the same level as in GaSb and above the valence bands in InxGa1-xAs (0

The electronic properties of hydrogenated silicene and germanene, so called silicane and germanane, respectively, are investigated using first-principles calculations based on density functional theory. Two different atomic configurations are found to be stable and energetically degenerate. Upon the adsorption of hydrogen, an energy gap opens in silicene and germanene. Their energy gaps are next computed using the HSE hybrid functional as well as the G0 W0 many-body perturbation method. These materials are found to be wide band-gap semiconductors, the type of gap in silicane (direct or indirect) depending on its atomic configuration. Germanane is predicted to be a direct-gap material, independent of its atomic configuration, with an average energy gap of about 3.2 eV, this material thus being potentially interesting for optoelectronic applications in the blue/violet spectral range. © 2011 American Institute of Physics.

The g-tensors of dangling bonds at defective Ge atoms in GeO2 are computed using density functional theory. The isotropic g-values of these defects are found to increase with the number of Ge backbonds. By comparing these calculations with the isotropic g-value of a Ge-related defect at Ge/GeO2 interfaces, recently observed by electron spin resonance and electrically detected magnetic resonance experiments, we tentatively identify this defect as a Ge2O Ge-center dot center, i.e. a dangling bond on a Ge atom backbonded to two Ge atoms and one O atom, likely present near the Ge/GeO2 interface. The interaction of this defect with molecular hydrogen is investigated using first-principles molecular dynamics simulations. Our simulations predict that the Ge dangling bond can be hardly passivated by H-2 molecules, in agreement with the electron spin resonance study.

The electronic properties of hydrogenated silicene and germanene, so called silicane and germanane, respectively, are investigated using first-principles calculations based on density functional theory. Two different atomic configurations are found to be stable and energetically degenerate. Upon the adsorption of hydrogen, an energy gap opens in silicene and germanene. Their energy gaps are next computed using the HSE hybrid functional as well as the G0W0many-body perturbation method. These materials are found to be wide band-gap semiconductors, the type of gap in silicane (direct or indirect) depending on its atomic configuration. Germanane is predicted to be a direct-gap material, independent of its atomic configuration, with an average energy gap of about 3.2 eV, this material thus being potentially interesting for optoelectronic applications in the blue/violet spectral range. © 2011 American Institute of Physics

The structural and vibrational properties of amorphous germanium oxide (a-GeO2) are investigated using first-principles calculations based on density functional theory. We first generate an a-GeO2structure by first-principles molecular dynamics and analyze its structural properties. The vibrational spectra is then calculated within a density-functional approach. Both static and dynamic properties are in good agreement with experimental data. We next generate defects in our structure (oxygen vacancies with several density and charge states) and consider the most stable atomic configurations, focusing on the vibrational features of threefold coordinated O and divalent Ge centers. © 2011 American Institute of Physics

The influence of the high temperature annealing ambient (N2 or Ar) on size controlled Si nanocrystals (NCs) in SiO2 ranging from ~2 to ~6 nm has been investigated in detail. Generally, N2 annealing is beneficial as the dangling bond density (Pb-defects at the NC/SiO2 interface) is about half accompanied by a doubled PL intensity. The N-related PL blueshift was found to be pronounced only for the small NCs whereas it appears to be insignificant for larger NCs. The origin of this N-blueshift was previously attributed to NC growth suppression by the presence of N. However, no evidence for this assumption is found by time-resolved PL, as the luminescence decay times are similar despite considerable N-blueshift. The exact location of the N incorporated during annealing was investigated by ToF-SIMS and ESR: Besides the distinct N-enrichment in the NC-layer, the K0-center (•Si≡N3) was detected indicating the formation of an interfacial N layer at the NC/SiO2 interface. ERD analysis enabled the quantification of the incorporated N as well as the excess Si. Combined with TEM analysis (determination of NC size) the calculation of the NC-density per superlattice layer and the thickness of the interfacial N-layer were achieved. It turns out that ~ 5×1014 N-atoms cm-2 exist at the NC, which is well in accordance to the optimum value of the bulk Si/SiO2 interface. These results support our recently suggested explanation for the N-blueshift that is based on the influence of the polarity of the surface terminating groups on the bandgap of the NC.

SiO2 is the most widely used dielectric material but its growth or deposition involves high thermal budgets or suffers from shadowing effects. The low-temperature method presented here (150 °C) for the preparation of SiO2 by thermal atomic layer deposition (ALD) provides perfect uniformity and surface coverage even into nanoscale pores, which may well suit recent demands in nanoelectronics and nanotechnology. The ALD reaction based on 3-aminopropyltriethoxysilane (APTES), water and ozone provides outstanding SiO2 quality and is free of catalysts or corrosive by-products. A variety of optical, structural and electrical properties are investigated by means of infrared spectroscopy, UV-VIS spectroscopy, secondary ion mass spectrometry, capacitance-voltage- and current-voltage-measurements, electron spin resonance, Rutherford backscattering, elastic recoil detection analysis, atomic force microscopy, and variable angle spectroscopic ellipsometry. Many features, such as the optical constants (n, k), optical transmission and surface roughness (1.5 Å) are found to be similar to thermal oxide quality. Rapid thermal annealing (RTA) at 1000°C is demonstrated to significantly improve certain properties, in particular by reducing the etch rate in hydrofluoric acid, oxide charges and interface defects. Besides a small amount of OH-groups and a few atomic per mille of nitrogen in the oxide remaining from the growth and curable by RTA no impurities could be traced. Altogether, the data point to a first reliable low temperature ALD-growth process for silicon dioxide.

Ge and III-V semiconductors are potential high performance channel materials for future CMOS devices. In this work, we have studied At. Layer Deposition (ALD) of high-k dielec. layers on Ge and GaAs substrates. We focus at the effect of the oxidant (H2O, O3, O2, O2 plasma) during gate stack formation. GeO2, obtained by Ge oxidn. in O2 or O3, is a promising passivation layer. The germanium oxide thickness can be scaled down below 1 nm, but such thin layers contain Ge in oxidn. states lower than 4+. Still, elec. results indicate that small amts. of Ge in oxidn. states lower than 4+ are not detrimental for device performance. Partial intermixing was obsd. for high-k dielec. and GeO2 or GaAsOx, suggesting possible correlations in the ALD growth mechanisms on Ge and GaAs substrates. [on SciFinder (R)]

Silicon dominates the electronics industry, but its poor optical properties mean that III–V compound semiconductors are preferred for photonics applications. Photoluminescence at visible wavelengths was observed from porous Si at room temperature in 1990, but the origin of these photons (do they arise from highly localized defect states or quantum confinement effects?) has been the subject of intense debate ever since. Attention has subsequently shifted from porous Si to Si nanocrystals, but the same fundamental question about the origin of the photoluminescence has remained. Here we show, based on measurements in high magnetic fields, that defects are the dominant source of light from Si nanocrystals. Moreover, we show that it is possible to control the origin of the photoluminescence in a single sample: passivation with hydrogen removes the defects, resulting in photoluminescence from quantum-confined states, but subsequent ultraviolet illumination reintroduces the defects, making them the origin of the light again.

Ge and III-V semiconductors are potential high performance channel materials for future CMOS devices. In this work, we have studied At. Layer Deposition (ALD) of high-k dielec. layers on Ge and GaAs substrates. We focus at the effect of the oxidant (H2O, O3, O2, O2 plasma) during gate stack formation. GeO2, obtained by Ge oxidn. in O2 or O3, is a promising passivation layer. The germanium oxide thickness can be scaled down below 1 nm, but such thin layers contain Ge in oxidn. states lower than 4+. Still, elec. results indicate that small amts. of Ge in oxidn. states lower than 4+ are not detrimental for device performance. Partial intermixing was obsd. for high-k dielec. and GeO2 or GaAsOx, suggesting possible correlations in the ALD growth mechanisms on Ge and GaAs substrates. [on SciFinder (R)]

An optical method is proposed for the calibration of pulsed magnetic fields using photoluminescence from synthetic diamond. Generally, the pulsed magnetic field profile is reconstructed by measuring the pick-up voltage in a small coil with an effective area that needs to be known accurately. A useful method to calibrate this area is presented using the 1.4040 eV optical transition at the 1.4 eV Ni-related centre in diamond. The field value is calculated from the Zeeman splitting of the optical lines using the g-factor previously characterized by electron spin resonance. Numerous advantages of the method presented are discussed.

An optical method is proposed for the calibration of pulsed magnetic fields using photoluminescence from synthetic diamond. Generally, the pulsed magnetic field profile is reconstructed by measuring the pick-up voltage in a small coil with an effective area that needs to be known accurately. A useful method to calibrate this area is presented using the 1.4040 eV optical transition at the 1.4 eV Ni-related centre in diamond. The field value is calculated from the Zeeman splitting of the optical lines using the g-factor previously characterized by electron spin resonance. Numerous advantages of the method presented are discussed.