摘要:

We have studied interfaces ofn‐InSb with SiO2films, obtained by low‐temperature chemical vapor deposition, using capacitance‐voltage measurements and Auger electron spectroscopy (AES). Improvements of electrical properties of MOS capacitors based on this system were sought by various pre‐ and post‐treatments. The results show that a methanol pre‐treatment causes significant improvements in the flat‐band voltage (VFB) of metal‐oxide‐semiconductor capacitors based on this system. In addition, thermal post‐annealing in oxidizing atmospheres also improvedVFB. AES reveals that at the SiO2‐InSb interface there is a native oxide interlayer, the width of which was found to be reduced by a factor of 2–3 due to the specified treatments. Therefore, we attribute theVFBimprovement to the reduction in the density of charges and traps due to the narrowing of the interfacial native oxide, in agreement with other recent results.

ISSN:0021-8979    

DOI:10.1063/1.340258

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The structural and electrical properties of twins in polycrystalline silicon materials have been investigated by electron‐beam‐induced current and transmission electron microscopy. The electrical activity of the first‐ and second‐order twins is related to segregation effects and to their structure, as described by geometrical models.

ISSN:0021-8979    

DOI:10.1063/1.340259

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Schottky junctions have been fabricated by evaporating aluminum on electrodepositedp‐type polycrystalline CuInSe2thin films. The devices showed a rectification effect with an ideality factor of about 2 in the low‐forward‐voltage region. Results of carrier concentration obtained fromC‐Vmeasurements of the Schottky devices were found to be consistent with those for CdS/CuInSe2heterojunctions fabricated on the same substrates. The apparent diffusion potential and carrier concentration of the Al/CuInSe2Schottky junctions were both found to increase after a short heat treatment at 200 °C in air.

ISSN:0021-8979    

DOI:10.1063/1.340260

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Several aromatic compounds (such as 3,4,9,10 perylenetetracarboxylic dianhydride) have previously been reported to form rectifying heterojunction energy barriers when vacuum deposited onto inorganic semiconductor substrates such as Si, GaAs, and InP. In this paper we report the formation of rectifying heterojunction barriers using phthalocyanine‐based compounds layered ontop‐Si substrates. In many respects, the characteristics of phthalocyanine/Si heterojunctions are similar to those formed using the aromatic anhydrides insofar as the electrical properties can be explained using the thermionic emission space‐charge‐limited transport model introduced in previous work. However, in contrast to the earlier results, we find that a high density of surface states exist at the phthalocyanine/Si interface. Quantitative study of the interface state density provides insight into the mechanisms of formation of the organic‐on‐inorganic energy barrier.

ISSN:0021-8979    

DOI:10.1063/1.340261

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Levitation of a magnet over a type II superconductor where the field at the superconductor exceeds Hc1is described and shown. The penetration and pinning of the flux lines in the superconductor cause the position of the magnet to be stable over a flat disk; a complete Meissner effect would make this position unstable. Furthermore, the observed dependence of the height of levitation on such variables as the thickness of the superconducting disk and the size of the magnet are consistent with a model described in this paper based on the energy cost of flux penetration through vortices and inconsistent with a Meissner effect model.

ISSN:0021-8979    

DOI:10.1063/1.340262

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Transmission electron microscopy is used to characterize the defects in highTcsuperconductor, Ba2YCu3O6.9produced by two different ceramic processing procedures. In both samples the microstructure is dominated by lamellar domains. These have been identified as reflection twins by observations both of rotations of the diffraction patterns and of &dgr;‐fringe contrast. The reflection plane is (110). The characteristic width associated with the twins correlates with annealing time. Occasionally within the twinned domain, substructure on a 50‐A˚ scale is visible, which is attributed to further subdivision into twinned and matrix domains. The twin structure does not interrupt the continuity of the Cu‐O planes between Y and Ba layers, but does terminate Cu‐O chains in the inter‐Ba Cu‐O planes. Convergent beam electron diffraction results are consistent with aPmmmspace group. Microcracks and disloction loops are also observed in the (001) basal plane, indicating that the (001) plane is both the slip and cleavage plane in this material.

ISSN:0021-8979    

DOI:10.1063/1.341149

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A nontrivial two‐dimensional stochastic model for dielectric breakdown within a parallel plate capacitor is presented for the first time. The model has been used to determine geometric properties of parallel plate discharges. Comparisons are made between these properties and known fractal properties of electrostatic discharges within cylindrical geometries. As the spacing between the plates of a capacitor increases, the value of the fractal dimension of the associated discharge structure increases from the minimum value of unity and approaches the limiting value corresponding to the case of infinite spacing. For any given spacing, this fractal exponent is equal to the exponent of first passage time for the discharge pattern to reach a given height. A study of various power law relationships governing the breakdown may provide insight into the breakdown mechanism and electrical insulating quality of various materials. The model is applicable to the breakdown of thin insulating layers of metal‐oxide‐semiconductor devices.

ISSN:0021-8979    

DOI:10.1063/1.340263

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The interface of a GaAs/AlxGa1−xAs heterostructure grown by metalorganic chemical vapor deposition has been studied by photoluminescence spectroscopy by using a step‐etching technique. Luminescence peaks associated with vacancy complexes emitted from both GaAs and AlxGa1−xAs layers were observed, and these peaks were remarkably intense on both sides of the GaAs/AlxGa1−xAs interface region. This result can be explained by the accumulation of vacancies in the interface region. The cause of this vacancy accumulation at the interface is discussed.

ISSN:0021-8979    

DOI:10.1063/1.340264

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A multiple quantum‐well structure grown by organometallic chemical vapor deposition and exhibiting a thickness gradient over the sample surface has been analyzed by spectroscopic and spatially resolved ellipsometry. The sample has been scanned in energy from 1.4 to 4.0 eV, with 5–10‐meV resolution, and in position over a 46‐mm line, with a 100‐&mgr;m optical resolution. Using multilayer modeling we have first determined the structural parameters and particularly the aluminum concentration in the barrier, and the barrier and the quantum‐well thicknesses. These two thicknesses vary from 95 to 10 A˚ along the 46‐mm scanned line, while their ratio as well as the aluminum concentration (64%) remain constant. The ellipsometric spectra, namely, the effective dielectric function which can be deduced from the tan &PSgr; and cos &Dgr; curves, allow for the determination of the multiple quantum‐well optical transitions around &Ggr;. In the thicker part of the wafer the optical spectra exhibit the well‐known feature of a multiple quantum well associated toN=1, 2, and 3 heavy holes → electron transitions. As the thicknesses decrease, the coupling between quantum well increases, and the structure becomes a superlattice. For a barrier thickness of 30 A˚, we observe the splitting of the fundamental level into two components: the first attributed to the symmetrical wave function and the second to the antisymmetrical wave function. The splitting is observed for both the heavy‐ and light‐hole transitions. As the coupling between wells still increases, the dielectric function of the superlattice tends towards the one of the GaAlAs alloy with an average aluminum concentration of 32%. The evolution of the optical transitions versus barrier and quantum‐well thickness has also been investigated theoretically by solving the Schro¨dinger equation for a periodic structure. The calculations have been done for two values of two conduction‐band offsets: 60% and 85%. The overall agreement between theory and experiment is very good for the 60% conduction‐band offset.

ISSN:0021-8979    

DOI:10.1063/1.340265

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A model for the optical absorption ofa‐Si:H/a‐SixN1−x:H multilayers has been developed which takes into account the effects of alloying in the interface regions between thea‐Si:H anda‐SixN1−x:H layers. Four different spatial variations of the film composition at the interfaces have been considered: abrupt, step, linear, and parabolic. The optical response of the interface regions is proposed to arise from Si‐centered tetrahedra, containing both Si and N atoms. Calculations of the dielectric function of the multilayer using the appropriate effective medium approximation have indicated that alloying at the interfaces leads to a lower optical absorption and a broadening of the multilayer absorption edge as compared to multilayers in which interface alloying is ignored. However, interface alloying apparently does not contribute appreciably to the observed increase in the optical energy gap of thea‐Si:H layer in the limit of decreasing layer thickness.

ISSN:0021-8979    

DOI:10.1063/1.340266

出版商:AIP    

年代:1988

数据来源: AIP