Metastable states in Si:H

The results of ab initio LDF calculations applied to large clusters of Si atoms containing H in various positions are described. We find the bond centred (BC) defect to be most stable for neutral and positively charged H. H placed at an antibonding site is also stable with an energy 0.1 eV higher than the BC defect. The stability of H₂ and H^*₂ is also discussed. New results are reported for the conversion of BC defects into Si dangling bonds. It is found that H attached to vacancy-like defects is bi-stable: for Si-H-Si lengths less than ≈3.8 Å, the BC defect is stable, whereas for longer separations, the Si-H ··· Si dangling bond is stable. A discussion of the relevance of this to the Staebler-Wronski effect is given.     

Surface photovoltage,band-bending and surface states on a-Si : H

We have measured the surface photovoltage (SPV) of intrinsic (i.e., undoped) and phosphorus-doped amorphous Si : H between ?168 and 25°C in the spectral range from 0.5 to 2.5 eV. The a-Si : H was grown in a silane glow discharge. Vibrating Kelvin probe techniques were used for the SPV measurements; Auger spectroscopy was used for monitoring surface cleanliness and chemistry. At all temperatures and for both materials, (1) the SPV was invariably negative, (2) there was no correlation between the spectral, thermal and response-time properties of the SPV and the bulk photoconductivity, and (3) surface treatments such as sputtering and oxygen physisorption strongly affected the SPV but not the photoconductivity. These facts indicated that the SPV was due to the emptying of surface-states via surface transitions, and corresponded to the flattening of bands which, when unilluminated, were bent upwards. Intrinsic material showed a maximum SPV of about 0.2 V. The SPV was characterized at ?168°C by strong electronic isolation between surface-states and valence band (i.e., once light was removed, there was no surface-state refilling or decay of the SPV), slow rise times (～min), saturation at photon fluxes of about 10¹¹/cm² · s, and a SPV spectral threshold occurring at 0.7 eV. At 25°C, all SPV responses were much faster (<0.5 s) and the optical threshold was 0.9 eV. The thermal activation energies associated with the SPV were 0.11 eV for surface-state emptying and 0.22 eV for surface-state refilling. For P-doped material the maximum SPV at ?168°C was 0.3 V and its properties indicated less electronic isolation between surface-states and valence band. There was no SPV at room temperature. Our results are discussed in terms of an energy level scheme which contains a distribution of filled surface states isolated from both conduction and valence bands. The surface-state density is estimated to be about (1?2) × 10¹¹/ cm², a relatively low value which is consistent with the observed lack of Fermi level pinning. In both materials there is a very fast component of the SPV which suggests the presence of additional surface states below the valence band edge.     

Coherent states,phase states,and condensed states

We study phase properties of generalized coherent states obtained from usual Fock coherent states by adapting classical methods of statistical mechanics, in particular, the well-known procedure of thermodynamical limit. Moreover, we show that there exists a close connection between these states and the states describing boson systems with condensation properties.     

H2NSi radical: structures,isomerization pathways and electronic states characterization

Using state-of-the-art theoretical methods, the stable isomers of H₂NSi which are relevant for astrophysics, astrochemistry and ammonia silicon surface chemistry, were investigated. These computations are performed using configuration interaction ab initio methods and the aug-cc-pVQZ and cc-pVQZ basis sets. Calculations confirm the existence of three stable isomers: H₂NSi, trans-HSiNH and H₂SiN. The intramolecular isomerization and the H-abstraction reaction pathways on the lowest doublet potential energy surfaces are given. Insight into the pattern of the lowest doublet and quartet electronic states of these molecular species are also presented.      

Bound ro-vibronic states of triplet H3(+)

On the basis of a new, highly accurate potential energy hypersurface for the lowest triplet state of H+3, (3)Sigma(+)(u), the bound ro-vibronic states are calculated for J相似文献   

Electronic states of C2H6 +

The complete photoelectron spectrum of ethane has been measured in the valence region using Ne, He I, and He II resonance radiation. The resolution of these spectra is sufficient to partially resolve vibronic structure accompanying the transition to the ground ionic state. The similarity of this structure with that obtained from model calculations using the Jahn-Teller theorem strongly suggests that the active vibration in this transition is a doubly degenerate CH₃ deformation mode and that the ground ionic state is a Jahn-Teller split ² E _g state. These experiments suggest a ² A _1g term for the first excited ionic state. The transition to the ² A _2u state of the ion contains evidence for two active vibrations v ₁ (C–H stretch) and v ₃ (C-C stretch).     

Model basis states for photons and "empty waves"

From the perspective of physical realism (PR), a photon is a localized entity that carries energy and momentum, and which is surrounded by a wave packet (anempty wave) that is devoid of observable energy or momentum. In creating quantized PR basis states for a photon wave packet, three requirements must be met:(1) The basis states must each carry the frequency of the wave;(2) They must closely resemble the photon, so that e.g. they scatter in the same manner from an optical mirror;(3) They must have infinitesimal energy, linear momentum, and angular momentum. An essentially zero-energy "empty wave" quantum-a "zeron"-is defined which meets these requirements. It is created as an asymmetric single-particle (or single-antiparticle) excitation of the vacuum state, with the "particle" (or "antiparticle") and its associated "hole" (or "antihole") forming a rotational bound state. The photon is reproduced as a symmetric particle-antiparticle excitation of the vacuum state, with the "particle" and "antiparticle" also forming a rotational bound state. The relativistic transformation problem is discussed. A key point in this development is the deduction of the correct equation of motion for a "hole" state in an external electrostatic field.