摘要:

We report preliminary results of scanning electron microscopy (SEM) imaging with submicron resolution at atmospheric pressure using silicon nitride windows to separate the atmosphere from the electron optics. The edge response of the current system is 0.25 μm through 75 nm windows at 15 μm air path length. We discuss the merits of windowed atmospheric SEM systems.

ISSN:0734-211X    

DOI:10.1116/1.585422

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A method is presented for performing attractive‐mode force potentiometry with submillivolt accuracy and a typical spatial resolution of order 50 nm. The technique permits measurements to be made in air on specimens which may be passivated or oxidized, conducting or semiconducting, with virtually no sensitivity to oxide thickness or character. An initial demonstration is presented showing voltage measurements on a commercial operational amplifier.

ISSN:0734-211X    

DOI:10.1116/1.585423

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A technique is described for the measurement of surface photovoltage (SPV) on semiconducting samples using the attractive‐mode scanning force microscope. The use of SFM potentiometry1permits microscopic measurement of surface photovoltage to be made in air with a spatial resolution of a few tens of nm and voltage resolution of better than 1 mV. Thus, with a spatial resolution only 1 order of magnitude worse than scanning tunneling microscopy measurements,2atomic force microscopy (AFM) is seen to be a good choice in measurements on devices or other structures where measurement under ambient is desirable or tolerable. Historically, SPV has permitted the observation of a wide range of features in semiconducting samples, including mapping of dopant concentration, sodium accumulation, local charge, dislocations, precipitates, stacking faults, grain boundaries and microcracks, local resistivity, recombination time, band gap shifts (for instance in heterostructures), and stress.3Experimental results will be presented which demonstrate the application of AFM/SPV to microcracking, dopant profiling and dislocation structure.

ISSN:0734-211X    

DOI:10.1116/1.585424

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

With a collection of images taken with the scanning tunneling microscope from the samples of several different organic and biological molecules adsorbed on graphite and/or gold substrates and covered with a very thin layer of 50% glycerol–water solution we show that covering such samples with the solution could facilitate imaging of them and improve the quality of images thus collected, and very often images with atomic resolution could be obtained.

ISSN:0734-211X    

DOI:10.1116/1.585425

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

We report on a study of nucleation and growth morphology of diamond microcrystals formed by microwave enhanced chemical vapor deposition. By doping diamonds with boron, sufficient conductivity is achieved that they may be directly imaged by scanning tunneling microscopy with near‐atomic resolution. We demonstrate the first application of work function anddI/dVimaging of diamond. These techniques offer the ability to identify nuclei too small to be recognized by their characteristic cubo‐octahedral shape, and may enable identification of nucleation sites before diamond growth begins.

ISSN:0734-211X    

DOI:10.1116/1.585426

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A new technique for the production of composite nano materials was used to produce carbon coated gold superfine particles in the 100 nm size range. Particles were produced in pulsed CO2laser (2 J/pulse at 3×109W/cm2) stimulated plasmas using solid Au targets and 1:3 mixtures of CH4, CO, or CO2with He or H2gases at 1.3 kPa pressure. The particle production rate was dependent on the presence and type of carbonaceous gas species, and the partial and total gas pressures. Thin films of the black superfine particles were deposited on glass, ceramic and metal substrates. X‐ray photoelectron spectroscopic analyses showed that Au was in the metallic state in the particles, both before and after thermal annealing, at an average concentration of 95% by mass. Fourier transform ion cyclotron resonance mass spectrometry of gaseous products emitted during thermal and laser anneals identified the major constituents as carbon dioxide and hydrocarbons. Scanning electron microscopy images of thermally annealed films showed that the particles retained their relatively uniform 100 nm diam size, despite significant changes in optical and electrical properties.This is attributed to loss of the carbon coating on the exterior of the Au particles. While some of the carbon is catalytically oxidized during thermal annealing, the majority remains in the bulk of the film, presumably concentrated at subsurface grain boundaries. Annealing the films in air produced sharp, permanent color changes to purple at 470 K and red/yellow at 493 K due to the loss of the carbon coating from the basic Au particle. Films deposited at 373 K on glass substrates were ∼5× more reflective in the 450–750 nm portion of the spectrum than films deposited at 300 K due to increased particle packing density. Particle films were also annealed using an unfocused CO2laser beam and a radio‐frequency field. A focused argon ion laser beam was used to anneal lines as narrow as 0.5 μm in particle films on glass substrates. The lowest sheet resistance value measured for an unannealed particle film deposited on glass at 298 K was 5600 Ω/square. Resistance versus temperature (in air) measurements across a 2 mm wide gap of a coated ceramic feedthrough exhibited minima of 9 mΩ at 450 K and 4.47 MΩ at 655 K, and a maximum of>20 MΩ from 493–600 K. The temperature dependent electrical and optical properties of the Au/C particle films, especially their high temperature stability relative to traditional gold blacks, make them potential candidates for applications in infrared optical systems.

ISSN:0734-211X    

DOI:10.1116/1.585427

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.585428

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.585429

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

WNX–Schottky diodes on semiconductor–insulator–semiconductor‐liken‐GaAs/undoped‐AlGaAs/n‐GaAs heterostructures have been fabricated at various annealing temperatures. The barrier characteristics are evaluated and compared with those of WNX–n‐GaAs Schottky contacts. At lower annealing temperatures the metal–insulator–semiconductor (MIS) like diodes exhibit superior barrier heights. However, at higher annealing temperatures (TA≥800 °C), both the MIS and WNX–n‐GaAs Schottky diodes almost have equivalent barrier heights. The ideality factors of the MIS like diodes are worse over the whole temperature range. Thicker undoped AlGaAs layers result in increased barrier heights at lower annealing temperatures (TA≤800 °C).

ISSN:0734-211X    

DOI:10.1116/1.585430

出版商:American Vacuum Society    

年代:1991

数据来源: AIP

摘要:

A mechanical probe for temperature measurements in the range 300–530 °C has been developed in order to control the substrate temperature in a molecular‐beam epitaxy system. In this temperature range conventional measuring devices like standard thermocouples and pyrometers do not provide the absolute temperature of the substrate. The probe makes contact with the substrate in a nongrowth position. To balance the heat flow from the sample holder to the probe, two thermocouples and a compensating oven are integrated with the probe. A reproducibility of ±2 °C can be achieved when measuring the absolute temperature.

ISSN:0734-211X    

DOI:10.1116/1.585431

出版商:American Vacuum Society    

年代:1991

数据来源: AIP