摘要:

The plasma deposition of nanocrystalline silicon thin films is usually performed under a high flux of atomic hydrogen and hydrogenated chemical species. The growth mechanisms are investigated using the layer‐by‐layer deposition of dense nanocrystalline silicon, obtained at 250 °C by alternating SiH4and H2plasmas. In the steady state, a minimum exposure time to the hydrogen plasma is necessary to recrystallize the amorphous top layer (10–85 A˚). It is shown that this critical time is determined by the diffusion time of some mobile H through the topa‐Si:H layer. The recrystallization is discussed in relation to the diffusion of hydrogen leading to the nanovoid and broken bond formation processes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113704

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A one‐dimensional ballistic constriction has been fabricated from a two‐dimensional electron gas formed at the interface of a GaAs/AlGaAs heterostructure. The constriction was induced via a pair of front gates which also served as a broadband far‐infrared (FIR) antenna. The photocurrent through the constriction was recorded as a function of source‐drain bias at various FIR frequencies, one‐dimensional subband spacings, and for orthogonal FIR polarizations. The photocurrent was compared to the derivative of dc conductance with respect to source‐drain bias. While dc rectification is shown to dominate the photocurrent, deviations from this model occur at frequencies above ∼1 THz, yielding an estimate of the upper limit of the electron scattering time in the constriction region. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113705

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The ground state atomic hydrogen density in a hydrogen/acetylene discharge is compared with the diamondlike carbon (DLC) film quality as determined frominsituellipsometry measurement of the refractive index. Two‐photon laser‐induced fluorescence (LIF) was employed for the detection of the ground state atomic hydrogen in the rf generated discharge. Absolute atomic hydrogen number densities were determined by calibrating the LIF detection system using a transfer standard. A direct correlation was found between the level of molecular hydrogen dissociation in the plasma and the refractive index of the DLC film. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113706

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This letter presents an experimental study, using high‐resolution atomic force microscopy, of the nature of the steps on the surface of GaInP layers lattice matched to GaAs substrates. The substrates were intentionally misoriented from the (001) plane by angles of 3°, 6°, and 9° toward [1¯10] and the layers were grown by organometallic vapor phase epitaxy at temperatures of 570, 620, and 720 °C. The surfaces consist of a mixture of monatomic (2.9 A˚) [110] steps and [110] oriented supersteps with a distribution of heights from 2 to approximately 17 monolayers. The height of the largest steps increases monotonically with increasing misorientation angle. The supersteps are apparently formed by bunching of monatomic steps producing high index (11n) surfaces (n=4 to 7). This leaves relatively large (several hundred A˚) (001) facets adjacent to the supersteps. The superstep height increases and the density decreases with increasing growth temperature. An attempt is made to correlate the supersteps to the degree of order and the microstructure of the ordered domains. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113707

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Fluorine was co‐implanted with 2 MeV erbium into silicon substrates. The thermal treatment for implanted samples was started with a 600 °C, 3 h anneal for solid‐phase epitaxial regrowth then followed by a 900 °C, 30 min anneal to optically activate the erbium atoms. Photoluminescence measurements have shown a strong enhancement of the luminescence intensity in samples co‐implanted with fluorine which, it is suggested, leads to the formation of Er–F complexes and facilitates defect annealing in the silicon lattice. Rutherford backscattering spectrometry was used to characterize the crystalline quality and erbium redistribution after the regrowth. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113708

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied the effects of monolayer coverage, V/III flux ratio and growth rate on the density of three‐dimensional growth induced isolated InAs islands grown on GaAs by molecular‐beam epitaxy. Within the isolated island growth regime, increasing the monolayer coverage increases the InAs island density with only a small increase in island size. Decreasing the V/III flux ratio or decreasing the growth rate increases the island density without changing the average in‐plane island diameter. We have observed island densities that are 80% of the ideal close‐packed island density. We propose a model explaining the island density increase with monolayer coverage; local variations in accumulated strain in the wetting layer vary the point at which local islanding is initiated. As more material is deposited more islands are nucleated and the island density increases. The island density increases with decreasing V/III flux ratio or growth rate by increasing the adatom surface diffusion in the underlying wetting layer, leading to a more uniformly strain wetting layer and a more uniformly roughened growth front. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113709

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Experimental investigations of electron relaxation in the confinement region and capture into the quantum wells are reported for InGaAsP/InP laser structures. The measurements are performed by time‐resolved photoluminescence using upconversion. The value for the electron capture of 1.4 ps is obtained. No dependence on the potential profile of confining layers has been observed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113710

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The microscopic structures and binding energies of DX centers for column III and VII impurities in CdTe are determined through first‐principles total energy calculations. The ionic displacements leading to DX formation for column VII impurities in II‐VI semiconductors are found to be different than those for corresponding column VI impurities in III‐V semiconductors.Threedistinct types of structures with DX‐like properties are found for column VII donors. The relative stability of these structures is impurity and pressure dependent. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113711

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The Coulomb blockade region was measured directly in an experimental single‐electron memory device. The device was constructed with multiple‐tunnel junctions (MTJ) formed by making a sidegated constriction in &dgr;‐doped GaAs. The Coulomb blockade region is defined by electron transfer rates of less than 10 electrons per second. At low values of sidegate voltages in the MTJ an enhancement of the Coulomb blockade is observed and explained by the formation of a nonuniform electrostatic potential in the semiconductor tunnel junctions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113712

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The evolution of the electrical activation with the annealing time in B+implanted (5.0×1014cm−2, 50 keV) Si was studied as a function of the annealing temperature. Electrical activation yields of 15%–30% were observed after annealing for 2 s at temperatures above 550 °C. Prolonging the annealing time from 2 to 900 s we observed that the electrical activation evolves differently according to the temperature: (i) at 550 °C<T<700 °C it decreases toward an equilibrium level, (ii) at 700 °C<T<800 °C it decreases during the first minutes and subsequently increases again, and (iii) at temperatures <550 °C orT≳800 °C it increases continuously. In order to explain the carrier removal observed during annealing at 550–800 °C we proposed that metastable acceptor centers are formed during the B+implantation and/or the initial period of the annealing time. Interaction of Si self‐interstitial atoms with these centers leads to their neutralization and/or dissociation with consequent decreasing of the carrier concentration. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113713

出版商:AIP    

年代:1995

数据来源: AIP