Piezospectroscopy

D. Heiman, Spectroscopy of Semiconductors at Low Temperatures and High Magnetic Fields A. V. Nurmikko, Transient Spectroscopy by Ultrashort Laser Pulse Techniques A. K. Ramdas and S. Rodriguez, Piezospectroscopy of Semiconductors O. J. Glembocki and B. V. Shanabrook, Photoreflectance Spectroscopy of Microstructures D. G. Seiler, C. L. Littler, and M. H. Wiler, One- and Two-Photon Magneto-Optical Spectroscopy of InSb and Hgj Cd Te... 

A detailed presentation of the piezospectroscopy of semiconductors can be found in [124]. Uniaxial stress is the most easily-produced perturbation (for experimental details, see Sect. 4.7.1), and the spectroscopy performed under stress is called piezospectroscopy. The relevant piezospectroscopic parameters for an impurity line are the number of components observed, their polarization characteristics and the amplitude of their shifts and splitting as a function of the value of the stress. Piezospectroscopy is useful when studying degenerate electronic transitions of the EM-like centres as it can lift intrinsic degeneracy. It can also lift the orientational degeneracy of electronic (and vibrational)... 

Photoluminescence piezospectroscopy is an accurate measurement method to determine nanoscale stress distributions and surface defects that control device performance and reliability, that is performance over the service life of biomaterials such as hydroxyapatite coatings and implants. 

Raman photoluminescence piezospectroscopy of bone, teeth and artificial joint materials has been reviewed by Pezzotti (2005) with emphasis placed on confocal microprobe techniques. Characteristic Raman spectra were presented and quantitative assessments of their phase structure and stress dependence shown. Vibrational spectroscopy was used to study the microscopic stress response of cortical bone to external stress (with or without internal damages), to define microscopic stresses across the dentine - enamel junction of teeth under increasing external compressive masticatory load and to characterise the interactions between prosthetic implants and biological environment. Confocal spectroscopy allows acquisition of spatially resolved spectra and stress imaging with high spatial resolution (Green etal., 2003 Pezzotti, 2005 Munisso etal., 2008). 

Margueron, S. and Lepoutre, F. (2003) Determination des contraintes residuelles par piezospectroscopie dans les couches d alumine l interface des barrieres ther-miques./. Phys. IV, 106, 161-170. 

Figure 14 (A) energy levels in Af sites in a-alumina structure (B) the R1 and R2 lines of piezospectroscopy of alumina with and without stress.

Figure 15 (A) Frequency shift of photoluminescence piezospectroscopy (PLPS) measured at room temperature in the course of cyclic oxidation of EBPVD samples. (B) Progress of interfacial separation after different cycles at 1150°C. Redraw from [88],...

We shall describe in some detail the ideas behind the piezospectroscopy of the absorption coefficient of the indirect gap. 

Piezospectroscopy experiments in Si and GaP have made it possible to determine the ratio of Se-ph/Sh-ph for the I-A (X) transitions for several intervalley phonons, i.e. TO in Si and LA and TA in GaP. Comparing these results with experimental values and theoretical expressions for the absorption coefficient related to these phonon-assisted processes we have been able to... 

Although in Ge a piezospectroscopy experiment has been performed on the LA phonon-assisted transition its interpretation is more complex due to the fact that there are two intermediate electron states. However, from this work as well as the WMA spectrum of the TO-phonon assisted transition at zero stress valuable information about Sg pjj and S -ph both these transitions was obtained. 

The success of piezospectroscopy experiments in the above materials strongly suggests the application to other indirect gap binary semiconductors such as AlSb, AlAs, etc. as well as indirect alloy materials such as GaAlAs, GaAsP, etc. In addition, information about intervalley EP and HP scattering matrix elements could also be obtained from ultra high pressure experiments (such as in a diamond anvil cell) where a direct gap material, such as GaAs, can be made indirect. 

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