摘要:

This letter describes the development of a submillimeter wave gyrotron operating at the second harmonic of the cyclotron frequency. The observed frequency is 383 GHz, which corresponds to the wavelength of 0.79 mm, and the output power is about 1 kW. We believe that the frequency is a world record for a stable, long pulse gyrotron operation at the second cyclotron harmonic, without a competition with the operation at the fundamental. Comparisons with the simulation results are represented.

ISSN:0003-6951    

DOI:10.1063/1.103086

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The first time‐integrated root mean square (rms) emittance measurement of a pseudospark‐produced electron beam is presented. From a six‐gap pseudospark chamber with argon working gas, ∼10 Hz repetitive pulsed electron beams of average energy ∼20 keV, peak current ∼50 A, and pulse duration ∼10 ns are extracted into a drift tube. A typical value of measured rms emittance is found to be &egr;≊55 mm mrad, yielding a normalized rms emittance of &egr;n≊15 mm mrad. The normalized brightness of the beam is then estimated to beBn≊4×1010A/(m2 rad2).

ISSN:0003-6951    

DOI:10.1063/1.103087

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Using a scanning photothermal reflectance microscope we have observed a large enhancement of the modulated reflectance signal accompanied by a phase change of &pgr; in the region of a copper‐decorated grain boundary in silicon. A preliminary analysis of the data is given in terms of the thermal and plasma waves generated in the specimen. Orders of magnitude of recombination velocities of the surface and the boundary are determined in reasonable agreement with electrical measurements.

ISSN:0003-6951    

DOI:10.1063/1.103088

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

InxGa1−xAs films have been grown by molecular beam epitaxy on graphoepitaxially grown germanium films on nickel replica sheets fabricated from an anisotropic etched silicon (001) surface. The crystallographic and optical properties of the InxGa1−xAs films have been characterized. The crystallographic orientation of the heteroepitaxial InxGa1−xAs has a small deviation from the orientation of synthesized surface relief in the graphoepitaxial substrate. This deviation in the heteroepitaxial film is caused by misorientation of the crystallographic orientation during the graphoepitaxial growth of germanium. The energy gap of the InxGa1−xAs has also a slight deviation from the expected one. The mechanism and its evidence have been studied.

ISSN:0003-6951    

DOI:10.1063/1.103089

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

It is demonstrated that scanning tunneling microscopy (STM) images often contain three‐dimensional ghost images of the tunneling tip. These ghost images directly reflect the shape of the tip, as is proven by comparing them with tip indentations made in Si. Tip images appear as a set of identical protrusions, and have been observed regularly on Si surfaces annealed at 1200 K in ultrahigh vacuum. Imaging of rough surfaces may be fully dominated by this effect which can lead to incorrect image interpretations in STM and AFM.

ISSN:0003-6951    

DOI:10.1063/1.103090

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Gold atoms in an epitaxial film on mica are clearly visible in images obtained with an atomic force microscope (AFM). The measured lattice spacing of 3.0± 0.3 A˚ is consistent with previous scanning tunneling microscope images obtained in air and vacuum. Atoms are visible even if the sample surface, tip, and cantilever are submerged in water in a closed cell. Electrochemical studies of metal electrodes at atomic resolution may now be possible with the AFM.

ISSN:0003-6951    

DOI:10.1063/1.103091

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Intentional carbon doping of low‐pressure metalorganic chemical vapor deposition (MOCVD) grown InP has been attempted with a 500 ppm mixture of13CCl4in high‐purity H2, which has been used to obtain carbon‐acceptor concentrations as high as 1×1019cm−3in GaAs. Under growth conditions similar to those used for heavy carbon incorporation in GaAs, injection of13CCl4into the growth reactor during growth of InP did not produce any measurable change in the carrier concentration of the InP epitaxial layers or any change in the13C concentration above the13C background in secondary‐ion mass spectroscopy analysis. These results support previous low‐temperature photoluminescence measurements of high‐purity InP in which no residual carbon acceptor is observed under many growth techniques and growth conditions, and hence support the hypothesis that carbon is not incorporated in InP grown by MOCVD.

ISSN:0003-6951    

DOI:10.1063/1.103092

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We describe a new semiconductor heterostructure, configured into a bistable device that can be switched either optically or electrically. The two states between which switching occurs involve very different levels of charge accumulation in a quantum well channel, affecting both the photoluminescence spectrum and the vertical photocurrent. The agents in the switching mechanism appear to be hot carriers.

ISSN:0003-6951    

DOI:10.1063/1.103093

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A self‐consistent quantitative analysis of recent kinetic data on the role of di‐ and trisilane in the plasma‐induced deposition of amorphous silicon from monosilane confirms the conclusion that the dominant reactive intermediate responsible for the formation of di‐ and trisilane and, consequently, for the deposition of a high quality amorphous silicon is SiH2. The data show that the SiH3radical may play only a negligible, if any, role in this process.

ISSN:0003-6951    

DOI:10.1063/1.103221

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We present results which may resolve the recently reported discrepancy between the experimental and the calculated electric fields in the depletion region of undoped GaAs. The photoreflectance theory reportedly underestimates the electric field by nearly a factor of 2. We have found that changes in photoreflectance with laser pump penetration reveal the full character of the electric field over the entire depletion zone. It is often assumed that the built‐in surface potential produces a uniform electric field throughout a thin (100 nm) undoped layer of GaAs grown on top of a heavily doped energy pinning underlayer. Instead, it appears that the heavily doped underlayer provides a potential step at the interface. The step is separated from the surface depletion zone by a region of low electric field which is characteristic of the low fields found in thick, undoped GaAs with (2–4)×1014/cm3of unintentional impurities.

ISSN:0003-6951    

DOI:10.1063/1.103094

出版商:AIP    

年代:1990

数据来源: AIP