A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.

The structural and luminescence properties of porous silicon

http://nathan.instras.com/documentDB/paper-69.pdf

Porous silicon: a quantum sponge structure for silicon based optoelectronics

Titanium dioxide (TiO2 ) nanocrystals are prepared by a hydrolysis process of tetrabutyl titanate. Nanocrystal samples with various sizes of 6.8-27.9 nm are obtained after annealing from 100 to 650 °C. The crystal structures and the average particle sizes are examined using x-ray diffraction. Raman scattering was employed to investigate the evolution of the anatase phase in the nanocrystals during annealing. Phonon confinement and non-stoichiometry effects are responsible for the blueshift and broadening of the lowest-frequency Eg Raman mode. The influence of interfacial vibrations on the Raman linewidth is also discussed.

https://iopscience.iop.org/article/10.1088/0022-3727/33/8/305/pdf

Raman scattering study on anatase TiO2 nanocrystals

Local mechanical stress is currently an important topic of concern in microelectronics processing. A technique that has become increasingly popular for local mechanical stress measurements is micro-Raman spectroscopy. In this paper, the theoretical background of Raman spectroscopy, with special attention to its sensitivity for mechanical stress, is discussed, and practical information is given for the application of this technique to stress measurements in silicon integrated circuits. An overview is given of some important applications of the technique, illustrated with examples from the literature: the first studies of the influence of external stress on the Si Raman modes are reviewed; the application of this technique to measure stress in silicon-on-insulator films is discussed; results of measurements of local stress in isolation structures and trenches are reviewed; and the use of micro-Raman spectroscopy to obtain more information on stress in metals, by measuring the stress in the surrounding Si substrate is explained.

https://iopscience.iop.org/article/10.1088/0268-1242/11/2/001/pdf

Micro-Raman spectroscopy to study local mechanical stress in silicon integrated circuits

https://hal.archives-ouvertes.fr/hal-00120432/document

Raman Spectroscopy of Nanomaterials: How Spectra Relate to Disorder, Particle Size and Mechanical Properties

The effects of microcrystal size and shape on the one phonon Raman spectra of crystalline semiconductors

Raman spectroscopy is widely used to study the vibrational and structural properties of single crystals. More recently, in the fields of chemistry, physics, and engineering, interest in the properties of small objects has arisen. Small objects include microcrystalline materials, artificially layered semiconductor structures, and colloidal suspensions. The reason for this recent interest is that these objects often display unique electronic properties which may find applications in devices. Since Raman spectroscopy is a convenient nondestructive tool, it is not surprising that it has been used to characterize such objects. In this review, we consider almost exclusively results obtained with semiconductors.

Raman spectroscopy of low-dimensional semiconductors

Using a conventional rf glow discharge, we have grown microcrystalline p+ SiC:H films having conductivities 2–2×10−3 (Ω cm)−1 and activation energies 0.05–0.1 eV with carbon concentrations 0–6 at. %, respectively. Increasing the carbon content suppresses the microcrystallinity. The choice of substrate is crucial to initiating the immediate onset of microcrystalline growth in thin (∼200–400 A) films.

Properties of p+ microcrystalline films of SiC:H deposited by conventional rf glow discharge

We observe, for the first time, structural modifications that extend many microns beyond the area where laser‐induced damage is visible by high resolution optical microscopy. These modifications are recorded by a Raman microprobe, which is sensitive to stress and microcrystallinity.

Long range material relaxation after localized laser damage

Low‐power, cw laser irradiation of GaAs leads to the formation of solid arsenic at the sample surface and to the degradation of band‐gap photoluminescence (PL) efficiency. In situ Raman scattering and PL are used to measure the lattice and carrier temperature in addition to monitoring the arsenic formation and PL efficiency. Both effects are athermal, do not involve surface oxidation, and occur in n,p and semi‐insulating GaAs prepared by different growth techniques. These observations suggest that arsenic formation and PL decrease may both be the result of a nonradiative recombination process.

I. H. Campbell

Papers

The effects of microcrystal size and shape on the one phonon Raman spectra of crystalline semiconductors

Raman spectroscopy of low-dimensional semiconductors

Properties of p+ microcrystalline films of SiC:H deposited by conventional rf glow discharge

Long range material relaxation after localized laser damage

cw laser irradiation of GaAs: Arsenic formation and photoluminescence degradation