摘要:

Near infrared Brillouin scattering was used to determine all three elastic constants, and hence Poisson’s ratio &ngr;=C12/(C11+C12) of epitaxial AlxGa1−xAs layers on GaAs. The AlxGa1−xAs layers were grown by metalorganic chemical vapor deposition and molecular beam epitaxy. We found evidence for a slight bowing in all elastic constants versus Al compositionx. The elastic constants of AlAs were determined to beC11=119.9 GPa±1.2 GPa,C12=57.5 GPa±1.3 GPa, andC44=56.6 GPa±0.7 GPa. From x‐ray measurements and the Poisson ratio &ngr;=0.324±0.004 the relaxed (cubic) AlAs lattice constant is found to beaAlAs=5.661 72 A˚±0.000 08 A˚. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114098

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

PbTiO3thin films have been prepared on Si/SiO2substrates by radio frequency planar magnetron sputtering technique. The target used in this experiment consists of multilayers of PbO and TiO2obtained by tape casting and cold pressing. The composition of the film is easily controlled by the thicknesses of the PbO and TiO2layers and also by the surface erosion. Target design and preparation, growth parameters and annealing conditions have been optimized to obtain stoichiometric films in the tetragonal crystal structure without second phase. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114099

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The influence of the addition of nitrogen on the phosphorus incorporation into and the growth rate of epitaxial diamond films grown by hot filament chemical vapor deposition, using a solid compound (NH4H2PO4) as a doping source, was investigated. Experiments show that the introduction of nitrogen gas into the system increases both the segregation of phosphorus in the epitaxial diamond and the film growth rate. The enhancement of phosphorus incorporation was attributed to the local lattice dilatation caused by a significant level of nitrogen dopant, while the increase of growth rate was explained by a model for defect‐induced stabilization of diamond. From the secondary ion mass spectrometry analysis, it was found that the effective incorporation efficiency of nitrogen in diamond is about 9×10−4. For phosphorus it can reach a value as high as approximately 1×10−3when a large amount of nitrogen is introduced simultaneously to the system. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114100

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Internal friction has been measured between 300 and 800 K on thin platinum films using a vibrating reed device. The 575 and 1500 A˚ thick samples were deposited with ion assistance on silicon substrate. It has been shown that the damping level is considerably reduced by annealing between 650 and 800 K. Thanks to isothermal experiments, we have determined the activation enthalpy of the process involved in the present structural evolution. The calculated energies and complementary transmission electron microscopy micrographs let us assume that the observed mechanism is closely related to microstructural rearrangements located at grain boundaries. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114101

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a simple technique of measuring surface temperature contrast with submicron spatial resolution. The technique uses the atomic force microscope (AFM) to scan a composite cantilever probe made of a thin metal film (aluminum or gold) deposited on a regular silicon nitride AFM probe. During tip‐surface contact, heat flow through the tip changes the cantilever temperature which bends the cantilever due to differential thermal expansion of the two probe materials. An ac measurement is used to separate cantilever bending due to temperature and topography. To eliminate image distortion due to air heat conduction, thermal images of a biased resistor were obtained in vacuum (10−5Torr). The images showed hot spots due to current crowding around voids in the heater and suggested a spatial resolution of 0.4 &mgr;m. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114102

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The field dependence of the dielectric constant of SrTiO3is investigated using the capacitance versus bias voltage characteristics of various metal‐SrTiO3:Nb Schottky diodes. The relative dielectric constant is shown to decrease one order of magnitude for electric fields ranging from 0.1 to 10 MV/cm. At low fields the permittivity follows the Curie–Weiss law, whereas at fields larger than 500 kV/cm the permittivity is nearly temperature independent. At high doping densities the field dependent permittivity gives rise to a reduction of the depletion width of the Schottky diode. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114103

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Real time ellipsometry and atomic force microscopy (AFM) were used to measure critical nucleation parameters for polycrystalline silicon deposition on an amorphous SiO2layer by rapid thermal chemical vapor deposition (RTCVD) using disilane (5% in helium). A particularly important parameter for selective epitaxial deposition is the time for nuclei to form, the incubation time. Quantitation of the nucleation parameters, such as the nuclei density, nuclei growth rate, nuclei coalescence, and an operational incubation time were determined from the real time ellipsometric measurements and confirmed by AFM. For a substrate temperature of 700 °C and at a chamber pressure of 0.2 Torr, the nuclei densities of 1.4×1010nuclei/cm2, incubation time of 26 s and nuclei layer growth rates of 20 nm/min were obtained. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114104

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using the atomic force microscope (AFM), we have fabricated a metal oxide semiconductor field‐effect transistor (MOSFET) on silicon with an effective channel length of 0.1 &mgr;m. The lithography at the gate level was performed with the scanning tip of the AFM. The gate was defined by electric‐field‐enhanced selective oxidation of the amorphous silicon gate electrode. The electrical characteristics were reasonable with a transconductance of 279 mS/mm and a threshold voltage of 0.55 V. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114105

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

It is shown that the electrode impedance can be separated from the bulk impedance in semiconductors and electrochemical cells using high dc biases. This is true both for two‐point dc resistance measurements and for two‐point ac impedance measurements. Experimental evidence on semiconductor thin films is presented. The dc biases required may be high, in the 50 V range, and can then be applied mainly to high resistance samples, in particular to thin films. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114106

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Micrometer‐sized homojunction structures can be formed by local application of strong electric fields (∼106V/cm) at ambient temperatures to Si which was homogeneously dopedn‐type by Li. Such junctions show electroluminesence and two such junctions, arranged back to back, act as transistors, as evidenced by electron beam induced current, current‐voltage and capacitance‐voltage measurements. These results are explained by thermally‐assisted electromigration of Li. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114107

出版商:AIP    

年代:1995

数据来源: AIP