This survey deals with 1/f noise in homogeneous semiconductor samples. A distinction is made between mobility noise and number noise. It is shown that there always is mobility noise with an /spl alpha/ value with a magnitude in the order of 10/sup -4/. Damaging the crystal has a strong influence on /spl alpha/, /spl alpha/ may increase by orders of magnitude. Some theoretical models are briefly discussed none of them can explain all experimental results. The /spl alpha/ values of several semiconductors are given. These values can be used in calculations of 1/f noise in devices. >

1/f Noise Sources

The purpose of this work is surface characterization of GaAs solar cell using atomic force microscopy. The surface appearance influences the optical properties of the cells. It impacts light trapping and consequently affect the efficiency of the solar cells. In case of nano-structural surface, the properties are strongly depends on its geometrical characteristics. Surface appearance was studied by atomic force microscopy (AFM). Fractal analysis was done by the triangulation method and evaluation of statistical metrics was carrying out on the basis of AFM-data, before and after heating. The results of fractal analysis show the correlation of fractal dimension and statistical characteristics of surface topography. Characterization technique and data processing methodology are essential for description of the surface condition.

Micromorphology investigation of GaAs solar cells: case study on statistical surface roughness parameters

Performance analysis of GaAs based solar cells under gamma irradiation

Degradation analysis of GaAs solar cells at thermal stress

Structural monitoring and assessment of an ancient masonry tower

A variety of microstructural defects in crystalline silicon solar cells

This paper describes our new improved set-up for EME and AE signals measurement and includes some experimental results. This new measurement system is based on the PXI platform, which is one of the most extended modular platforms for measurement and automation systems. The complex program package in the LabVIEW graphical programming environment was developed for the continual multi-channel EME and AE signals measurement, real time processing and evaluation. It offers the possibility to observe the stressed materials response to applied mechanical load in real time.

Electromagnetic and Acoustic Emission Signals Real-Time Measurement, Processing and Data Evaluation

Conducted loading tests of plain concrete specimens are briefly introduced in the paper together with description of the performed numerical simulations of these tests in ATENA 3D software. The simulation results of concrete failure are analysed in detail and compared with the experimental results recording failure processes with the help of acoustic emission. The simulation results are in good agreement with the recorded data.

Acoustic Emission from Quasi-Brittle Failure of Cementitious Composites - Experimental Measurements and Cohesive Crack Model Simulations

Laboratory tests on a wide range of solid materials shoved that the electromagnetic emission (EME) signals are generated during the samples mechanical stress. EME anomalies have been observed also under natural conditions in association to fracture processes, tectonic loading, stress redistribution and crack propagation prior to earthquake or in relation to deep-seated gravitational mass movements. This paper describes a first prototype of the Emission data logger, which was specially developed for the continual EME monitoring in field conditions. Our equipment has been installed and tested in Obir Caves (Austria) at an active tectonic fault. The pilot long-term EME measurement results from this location are also presented in this paper.

Field Measurement of Natural Electromagnetic Emissions near the Active Tectonic and Mass-Movement Fractures in Caves

The paper is focused on the utilization of electromagnetic emission (EME) and acoustic emission (AE) phenomena within the non-destructive assessment of damage and fracture in cementitious composites. In the first part of the paper, the EME and AE responses from tests performed in two testing configurations differing considerably in stress distribution are investigated. Typical EME and AE response waveforms appear not to differ from each other for either of the loading configu-rations. However, a significant difference is observed in the frequency distribution of the time lag of the acoustic signal behind the electromagnetic one, which results from the different distribution of the fracture events over the specimen’s volume. In the second part of the paper, the failure process within the specimens in the used testing configurations is assessed from the fracture-mechanical point of view. A numerical 3D analysis of the stress distribution and crack propagation within the specimens was performed by using ATENA non-linear FEM code based on a fracture- and damage-mechanics, and plasticity approach. The predictions of the numerical model are in good agreement with the results obtained by AE/EME experimental measurements. The comparison of the AE/EME records from the tests with the results of performed numerical simulation can help in the understanding, interpretation and exploitation of AE/EME in research into damage to and failure of non-electric quasi-brittle silicate-based building materials.

Pavel Koktavý

Papers

A variety of microstructural defects in crystalline silicon solar cells

Electromagnetic and Acoustic Emission Signals Real-Time Measurement, Processing and Data Evaluation

Acoustic Emission from Quasi-Brittle Failure of Cementitious Composites - Experimental Measurements and Cohesive Crack Model Simulations

Field Measurement of Natural Electromagnetic Emissions near the Active Tectonic and Mass-Movement Fractures in Caves

Utilization of Electromagnetic and Acoustic Emission in Monitoring of Fracture of Cementitious Composites