摘要:

Dry etching and consequent burring regrowth using anin situultrahigh vacuum multichamber system were investigated for nanometer-size fine patterns. Narrow stripe patterns with width variations from 30 to 5000 nm were fabricated on GaAs/AlGaAs single quantum wells using electron-beam lithography. The wafer was then etched and regrown in anin situmultichamber system. Using thisin situprocess along with a H-plasma treatment before regrowth, the surface nonradiative recombination velocity was able to be greatly reduced to6.8×104 cm−1from that of as-etched wafers(1.9×105 cm−1)estimated by measuring time-resolved photoluminescence (PL). Also, the size dependence of the PL intensity was able to be greatly improved to a degree that exceeded the InGaAs/InP wafers.

ISSN:1071-1023    

DOI:10.1116/1.589779

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

ZnTe nanoparticle-doped glass thin films which have quite unique anisotropies in microscopic structures and in optical properties in the thin film plane were fabricated by introducing ZnTe into nanometer-scaled voids included in well-known columnar structures of obliquely depositedSiO2films. ZnTe andSiO2were simultaneously deposited on substrates from two opposing oblique directions and then the samples were annealed. The samples consisted of two kinds of portions with planar shape; the portions of amorphous ZnTe (as-deposited samples) or condensing ZnTe nanocrystallites (postannealed samples) were stacked alternatively withSiO2portions in the thin film plane in the direction parallel to the plane including the two deposition directions. In-plane anisotropies in the refractive indices, the absorption coefficients, and the third-order nonlinear optical susceptibilities were evaluated. The anisotropies in the optical properties were revealed to be due to the fact that the distribution of the electric field of the incident light in the composite (inhomogeneous) samples depends on the polarization because of the structural anisotropy.

ISSN:1071-1023    

DOI:10.1116/1.589839

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Electroluminescent devices have been fabricated by depositing Al-doped ZnSTe onto GaAs substrates by molecular beam epitaxy. A moderately bright blue-light emission was observed at room temperature. Electroluminescence spectra reveal that light emission is mostly from impact excitation of Te isoelectronic centers in these structures. Surface morphologies and concurrent current images by using conducting atomic force microscopy indicate electrical inhomogeneity in such structures. Nonuniform light emission may be inferred from nonuniform current distributions on the submicrometer scale.

ISSN:1071-1023    

DOI:10.1116/1.589771

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

The recently developed, novel superhard nanocrystalline compositesnc-TiN/a-Si3N4have been investigated by means of high resolution transmission electron microscopy. The microstructure consisting of nanocrystalline TiN imbedded withina⩽1 nmthin amorphousSi3N4,the relative amount of both phases, and the TiN-crystallite size which were previously determined by means of x-ray diffraction and energy dispersive analysis of x rays have been directly confirmed.

ISSN:1071-1023    

DOI:10.1116/1.589778

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

A photometric field-emission electron microscopy technique is described by which the spatial structure of the surface electronic tunneling barrier can be mapped with nanometer resolution. The technique involves performing a Fowler–Nordheim analysis on luminosity data extracted from a set of digitized field-emission images taken over a range of voltages. This approach is equivalent to older probe-hole methods, but with greatly improved spatial resolution and data accumulation rate. Virtual probe holes of arbitrary size and shape can be constructed by integrating over subregions in the field-emission images. Performance of a system utilizing this technique is demonstrated by measuring the work functions of the (111) and (100) crystallographic planes of a clean tungsten field emitter. Applications of this technique to adsorption phenomena and field-emission display technology are also discussed.

ISSN:1071-1023    

DOI:10.1116/1.589787

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We report the first atomic resolution scanning tunneling microscopy (STM) images of S overlayers on the Fe(111) surface. S overlayers were obtained by annealing the Fe(111) crystal to elevated temperatures to induce the segregation of S from the bulk. STM images of the (1×1)-S structure are consistent with the proposed model of one “geometric” monolayer of S atoms occupyingon-topthree-fold hollow sites of the Fe(111) surface. The STM data also revealed the presence of nanoscopic triangular pits on the (1×1)-S surface. These pits are only one atom deep. Increased segregation of S results in the formation of a (2√3×1)R30° structure and an increase in the size and depth of the triangular pits. This new structure corresponds to S coverage corresponding to more than one “geometric” monolayer of S based on one geometric monolayer coverage for the (1×1)-S structure. STM images obtained within large pits reveal a periodic “staircase” topography consisting of terraces with (111) orientation. These terraces are made up of five atomic rows (14 Å) separated by monatomic steps. Images obtained on flat areas in between large pits reveal surface buckling. Two different packing arrangements of surface buckling were observed both consisting of vertically displaced atomic rows with a 14 Å periodicity, identical to the terrace widths of the staircase surface found inside large triangular pits. We propose that additional segregation of S to the (1×1)-S phase to form the (2√3×1)R30° structure involves the segregation of S to thesubsurfacethree-fold hollow sites on the Fe(111) surface. The close proximity of S atoms located aton-topandsubsurfacethree-fold hollow sites can result in strong S–S repulsive interactions which consequently drives the surface to undergo structural changes, similar to other reported adsorbate-induced faceting of bcc(111) surfaces.

ISSN:1071-1023    

DOI:10.1116/1.589801

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We show that a lubricant-coated tip produces less specimen damage when soft materials are observed by atomic force microscopy (AFM). We measured the adhesion force and obtained AFM images of bacteria flagella using the same silicon nitride tip untreated, cleaned, and lubricant coated (in that order). The results show that a lubricant coating reduces the adhesion force. This result and contact angle measurements for a lubricant-coated silicon nitride wafer show that the tip surface is made hydrophobic by the lubricant coating. Since the dominant factor in the adhesion force in air is water capillary force, the lubricant coating on a tip reduces the adhesion force and hence the specimen damage. A lubricant coating on the tip is effective for AFM imaging of soft materials, such as biological specimens.

ISSN:1071-1023    

DOI:10.1116/1.589819

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Atomic force microscopy is a versatile tool for ultrasensitive measurement. We explore the fundamental and practical limits to force sensitivity that are imposed by optical and electrical deflection sensing techniques, and present a method for designing cantilevers to optimize force sensitivity. We calculate the optimized force sensitivity to be1.2×10−18  N/ Hzat a temperature of 4 K, using a gallium arsenide piezoresistive cantilever with dimensionsw=0.1  μm,t=0.1  μm, andL=81  μm, and mechanical quality factorQ=104. The optimized force sensitivities obtained using silicon piezoresistive and optical detection are not far behind.

ISSN:1071-1023    

DOI:10.1116/1.589827

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

Thermal drift is frequently encountered when imaging with scanning probe microscopes. The drift skews real space images and distorts the reciprocal space lattice vectors. A settling time of up to 2 h is generally required to achieve relatively drift free images at the high magnifications needed for molecular or atomic resolution. We demonstrate a simple method to extract accurate lattice parameters from periodic samples which compensates for drift to first order (approximately constant drift rate), dramatically shortening the necessary waiting time. The method is based on averaging the apparent reciprocal lattice vectors corresponding to consecutive scans obtained in opposite scanning directions.

ISSN:1071-1023    

DOI:10.1116/1.589834

出版商:American Vacuum Society    

年代:1998

数据来源: AIP

摘要:

We present a novel method for the fabrication of generic scanned-probe microscope probes by performing multiple level direct-write electron-beam lithography on the apex of micromachined atomic force microscope tips. Pattern transfer is by conventional etching or liftoff in a wide range of materials. Lithographic resolution is 50 nm or better. The substrates support the use of automatic alignment and allow for the fabrication of50 probes/in2.The integration of a force-sensing cantilever permits simple height regulation of the probes during operation. The technology is illustrated by the fabrication of thermocouple and near-field optical probes.

ISSN:1071-1023    

DOI:10.1116/1.589835

出版商:American Vacuum Society    

年代:1998

数据来源: AIP