摘要:

Photoemission experiments performed on amorphous and crystalline GroupIVandIII–Vsemiconductors are reviewed. The relationship of the core level spectra of the compound semiconductors to the current structural models is discussed.

ISSN:0094-243X    

DOI:10.1063/1.2945995

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

We examine the effects of like atom bonds on the electronic density of states (DOS) of amorphous binary compounds. This is done explicitly using the empirical pseudopotential method to study various complex crystalline structures with different fractions of like‐atom bonds distributed in varying configurations. Our results show marked differences in the regions in the DOS that are most affected by like‐atom bonds. In particular we sketch the DOS of a typical amorphous system with 10% like‐atom bonds and show a plot of the charge density of a like and unlike atom bond.

ISSN:0094-243X    

DOI:10.1063/1.2945996

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The results of recent model density of states calculations and photoemission experiments for systems having many like‐atom bonds will be discussed to elucidate the effects of bonds between like atoms on the electronic density of states. It will then be argued that while recent photoemission results exclude the existence of large numbers of like‐atom bonds in amorphousIII–Vsemiconductors, they may not have the sensitivity to detect the small number of such bonds expected from random network models.

ISSN:0094-243X    

DOI:10.1063/1.2945997

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Photoemission energy distributions N(E,&ohgr;) were taken as a function of both electron energy E and photon energy ℏ&ohgr; using synchrotron radiation. Various spectral features associated with critical points in both the valence and conduction bands evident in crystalline Ge are absent in amorphous Ge. Features observed for amorphous Ge include: valence p‐bands about 4.2 eV wide with a peak at ∼ 1.4 eV below the valence band edge Ev, an overall valence bandwidth of ∼ 11.6 eV, and a conduction band state density peak at ∼ 2.3 eV above Ev.

ISSN:0094-243X    

DOI:10.1063/1.2945998

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The structure of amorphousSiOthin film is investigated by means of X‐ray photoelectron spectroscopy. Core electronbinding energies are determined for Si,SiOandSiO2. The problems of charging effects and reference level are discussed. Chemical shifts of Si2p and Si2s electrons are reported for these compounds. ForSiOthe Si photoelectron lines show a doublet structure. It is demonstrated thatSiOis not a mixture of Si andSiO2but may have a definite structure with two unequivalent chemical sites for Si. These ESCA results are interpreted according to the molecular structure model ofSiOsuggested by other physical properties.

ISSN:0094-243X    

DOI:10.1063/1.2945942

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The valence‐band density of states and the energies of the core levels of amorphous Ge alloys with X‐ray photoemission technique have been measured. The difference between X‐ray photoemission spectra from amorphous Ge‐Ni and Ge‐Fe alloys is discussed in connection with the results obtained from the measurement of the resistivity, magnetic susceptibility, ferromagnetic resonance and thermopower.

ISSN:0094-243X    

DOI:10.1063/1.2945943

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The energy loss spectra of monoenergetic 25 keV electrons having passed thin amorphous Ge and Si films are characterized by discrete and continuous energy losses. High energy resolution (0.005 eV) enables the observation of phonon excitation between 0.025 and 0.15 eV. In the region of the gap (0.15 to 0.5 eV) numerous peaks, corresponding to excitation of localized states were found. The principal maxima of localized states are located in a‐Ge at 0.210 and 0.365 eV and in a‐Si at 0.200, 0.255, and 0.360 eV. Interband transitions of a‐Ge were studied up to 3.0 eV.

ISSN:0094-243X    

DOI:10.1063/1.2945944

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

CubicZnShas been used as a model substance to study the influence of long range order vs short range order on the electronic spectrum. Energy bands, wave functions and scattering phases as well as the sensitivity on potential variations have been studied for crystallineZnS. It is found that there are certain states which effectively are determined by l.r.o., whereas others are mainly due to the atomic potentials. Comparison with CBS calculations shows that the latter are virtually unchanged in the amorphous phase.

ISSN:0094-243X    

DOI:10.1063/1.2945945

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A study of the plasma sum rules suggests that the oscillator strength for transitions from initial s‐p states in a‐Ge and a‐Si is reduced significantly compared with crystalline excitations, and is displaced to energies beyond the plasma frequency. Since p‐state transitions are essentially unchanged, the matrix element cannot be the same for all transitions, as has been assumed. A model is presented which makes a first attempt at accounting for the necessary electron energy dependence by considering transitions from the upper two p‐like states independent of excitations from the deeper s‐p states. The model is applied to a‐Ge;if the simplest different form is chosen for s‐p transitions, a substantially better agreement with experiment is achieved. We conclude that there is a substantial change in the character of s‐p states in going to the amorphous phase, thereby demanding that the electron energy dependence for optical transitions be considered.

ISSN:0094-243X    

DOI:10.1063/1.2945946

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Kramer's Complex Band Structure Model, which has been used to describe optical properties of amorphous semiconductors, has been improved by introducing an effective pseudopotential that takes into account characteristic distortions of the short range order of tetrahedrally bonded semiconductors. Numerical results on Ge andGaAsyield a simple explanation why the two lowest valence bands coalesce in Si and Ge and do not inIII–V‐compounds.

ISSN:0094-243X    

DOI:10.1063/1.2945947

出版商:AIP    

年代:1974

数据来源: AIP