Evolution of the Electron Acoustic Signal as a Function of Doping Level in III–V Compound Semiconductors

1988 ◽  
pp. 258-259
Author(s):  
J. F. Bresse ◽  
A. C. Papadopoulo
Keyword(s):  
Acoustic Signal ◽  
Doping Level ◽  
Compound Semiconductors ◽  
Electron Acoustic

Evolution of the electron acoustic signal as function of doping level in III‐V semiconductors

1988 ◽  
Vol 64 (1) ◽  
pp. 98-102 ◽  
Author(s):  
J. F. Bresse ◽  
A. C. Papadopoulo
Keyword(s):  
Acoustic Signal ◽  
Doping Level ◽  
Electron Acoustic

Evaluation of the electron acoustic signal generation in GaAs

1994 ◽  
Vol 27 (11) ◽  
pp. 2401-2413 ◽  
Author(s):  
K Kaufmann ◽  
K Orsech ◽  
M Domnik ◽  
L J Balk
Keyword(s):  
Acoustic Signal ◽  
Signal Generation ◽  
Electron Acoustic

Electron-acoustic microscopy-An overview

1983 ◽  
Vol 41 ◽  
pp. 6-9
Author(s):  
G. S. Cargill III
Keyword(s):  
Acoustic Signal ◽  
Signal Amplitude ◽  
Low Noise ◽  
Ultrasonic Waves ◽  
Acoustic Microscopy ◽  
Backscattered Electrons ◽  
Transducer Output ◽  
Video Amplifier ◽  
Electron Acoustic ◽  
Lock In

Electron-acoustic microscopy is a new way of to look at materials with a scanning electron microscope. Acoustic, or more properly ultrasonic, signals are detected instead of secondary or backscattered electrons. A SEM’s electron beam which is chopped at kHz or MHz rates serves as a localized periodic heat source for the specimen being examined, as illustrated in Fig. 1. Periodic thermal expansion in the specimen generates ultrasonic waves, which are detected by a piezoelectric transducer. Contrast in electron-acoustic images results mainly from spatial variations of thermal, elastic, and dimensional properties of the specimen, rather than from variations in surface topography or average atomic number.Additions to a conventional SEM for doing electron-acoustic microscopy consist of a beam chopping system, a well shielded transducer assembly on which samples are mounted, and electronics for using the transducer output to control the brightness of the SEM’s cathode ray tube (CRT) display, as shown in Fig. 2. Squarewave or sinewave voltages applied to beam deflector plates have been used for beam chopping. PZT transducers and quartz transducers have been used for detecting the acoustic signals. The transducer output, typically several microvolts, feeds a low-noise preamplifier, which drives either an rf amplifier-rectifier or a phase-sensitive (lock-in) amplifier/detector, and a video amplifier. Output of the video amplifier is used to control the CRT display brightness. The beam chopping signal is used as reference for the lock-in. Phasesensitive detection with a lock-in amplifier allows variations of acoustic signal phase as well as acoustic signal amplitude to be used in forming images.

Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 264-265
Author(s):  
D. R. Liu ◽  
S. S. Shinozaki ◽  
R. J. Baird
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Compound Semiconductors ◽  
Energy Dispersive Analysis ◽  
X Ray ◽  
Metastable Alloys ◽  
Lower Voltage

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.

Sign in / Sign up

Export Citation Format

Share Document