Local Vibrational Mode (LVM) Spectroscopy of Semiconductors

1995 ◽  
Vol 378 ◽  
Author(s):  
Eugene E. Haller
Keyword(s):  
Hydrostatic Stress ◽  
Thin Layers ◽  
Vibrational Modes ◽  
Semiconductor Crystal ◽  
Probe Light ◽  
Defect Complexes ◽  
Local Vibrational Mode ◽  
The Masses ◽  
Absorption Features ◽  
Impurities And Defects

AbstractImpurities and defects with masses smaller than the masses of the host semiconductor crystal atoms typically exhibit vibrational frequencies well above the phonon frequency spectrum. These vibrational modes produce sharp spectral absorption features in the infrared. Because of their strong spatial localization these modes are not affected by neighboring impurities and/or defects with concentrations up to 1019 cm−3. This insensitivity is especially advantageous when the free carrier concentration must be reduced through the introduction of electron irradiation defects or when highly doped thin layers must be investigated. LVM spectroscopy with perturbations such as polarization of the probe light, uniaxial and hydrostatic stress, and isotope substitution has been highly successful in identifying the structure and composition of a large number of defect complexes. Hydrogen, in particular, forming a wide variety of complexes in elemental and compound semiconductors has been extensively studied with LVM spectroscopy. For example, it has been shown recently that nitrogen acceptors are hydrogen passivated in MOCVD grown ZnSe. Carbon and oxygen have been investigated in all major semiconductors with LVM spectroscopy. The extreme simplification of the spectrum of bond centered oxygen through isotope enrichment of several Ge crystals has been demonstrated. Additional recent investigations of importance to the currently much studied semiconductors will be reviewed.

In situ irradiation effects studies in medium- and high-voltage TEM

1995 ◽  
Vol 53 ◽  
pp. 234-235
Author(s):  
Charles W. Allen
Keyword(s):  
Cross Section ◽  
Particle Flux ◽  
Threshold Value ◽  
High Energy ◽  
Irradiation Damage ◽  
Defect Complexes ◽  
Lattice Position ◽  
Electrons And Ions ◽  
The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

Hydrogen Local Vibrational Modes in Compound Semiconductors

1998 ◽  
Vol 513 ◽  
Author(s):  
M. D. Mccluskey
Keyword(s):  
Hydrostatic Pressure ◽  
Resonant Interaction ◽  
Host Lattice ◽  
Local Mode ◽  
Vibrational Modes ◽  
Temperature Dependent ◽  
Local Vibrational Mode ◽  
Combination Modes ◽  
Stretch Mode ◽  
Anharmonic Coupling

ABSTRACTLocal vibrational mode (LVM) spectroscopy of hydrogen and deuterium in GaP, AlSb, ZnSe, and GaN has provided important information about the structures of dopanthydrogen complexes and their interaction with the host lattice. In GaN:Mg, for example, hydrogen binds to a host nitrogen which is adjacent to the magnesium acceptor. In GaP and ZnSe, it has been demonstrated that the temperature dependent shifts of LVM's are proportional to the lattice thermal energy, a consequence of the anharmonic coupling of the local mode to acoustical phonons.Large hydrostatic pressures have been applied to semiconductors to probe the vibrational properties of hydrogen-related complexes. In GaAs, the pressure dependent shifts of the 12C-H and 13C-H stretch modes have positive curvatures, while the shift of the S-H stretch mode has a negative curvature. This may be related to the fact that in the bond-centered C-H complex, the hydrogen is compressed between the carbon acceptor and one gallium host atom, whereas in the S-H complex, the hydrogen occupies an interstitial position and is not crowded by neighboring atoms. If these trends are general, then hydrostatic pressure may be a powerful tool in determining the position of the hydrogen atom(s) in a complex.In AISb. pressure was utilized to resolve a mystery as to why the Se-D complex gives rise to one stretch mode peak while the Se-H stretch mode splits into three peaks. This anomalous splitting is explained in terms of a new resonant interaction between the stretch mode and combination modes involving a wag mode harmonic and extended lattice phonons. The interaction gives rise to vibrational modes with both localized and extended components. When the temperature or hydrostatic pressure is varied, the modes exhibit anti-crossing behavior.

scholarly journals The Trivacancy and Trivacancy-Oxygen Family of Defects in Silicon

2013 ◽  
Vol 205-206 ◽  
pp. 181-190 ◽  
Author(s):  
Vladimir P. Markevich ◽  
Anthony R. Peaker ◽  
Bruce Hamilton ◽  
S.B. Lastovskii ◽  
Leonid I. Murin ◽  
...  
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Minority Carrier ◽  
Vibrational Mode ◽  
Deep Level ◽  
Vibrational Modes ◽  
Carrier Injection ◽  
Local Vibrational Mode ◽  
Diffusion Paths ◽  
Transient Spectroscopy ◽  
And Diffusion

The data obtained recently from combined deep-level-transient spectroscopy (DLTS), local vibrational mode (LVM) spectroscopy and ab-initio modeling studies on structure, electronic properties, local vibrational modes, reconfiguration and diffusion paths and barriers for trivacancy (V3) and trivacancy-oxygen (V3O) defects in silicon are summarized. New experimental results on the introduction rates of the divacancy (V2) and trivacancy upon 4 MeV electron irradiation and on the transformation of V3 from the fourfold coordinated configuration to the (110) planar one upon minority carrier injection are reported. Possible mechanisms of the transformation are considered and discussed.

Thermal Anneal Effects on Carbon-Hydrogen LVMs In AlGaN

2001 ◽  
Vol 692 ◽  
Author(s):  
M. O. Manasreh ◽  
B. D. Weaver
Keyword(s):  
Thermal Annealing ◽  
Annealing Temperature ◽  
Chemical Vapor ◽  
Vibrational Modes ◽  
Defect Complexes ◽  
Maximum Value ◽  
Annealing Effects ◽  
Mocvd Technique ◽  
Subsequent Diffusion ◽  
Mg Doped

AbstractThermal annealing effects on carbon-hydrogen (C-H) complexes defects in AlGaN grown on sapphire by metalorganic chemical vapor deposition (MOCVD) technique have been investigated using Fourier transform infrared spectroscopy (FTIR). The CH complexes in AlGaN, formed either during growth or by proton irradiation, exhibit five local vibrational modes (LVMs) due to the symmetric and asymmetric vibrational stretching modes of C-H in CHn (n=1–;3) defect complexes. It was found that the annealing temperature (Ta) of 500°C is sufficient enough to dissociate most of the C-H complexes in AlGaN samples. A turning point annealing temperature is found around 300°C for un-irradiated Mg-doped sample, below which the total integrated area of the C-H LVMs continued to increase with increasing annealing temperature and reach the maximum value around 300°C. At Ta > 300°C, the total integrated area of the C-H LVMs starts to decrease and the C-H complexes seem to be completely depleted at Ta > 600°C. The depleted C-H LVMs were observed to partially recover after thermal annealing at Ta > 500°C and waiting for aging periods of several days. This recovery behavior is explained in terms of the hydrogen being remained inside the crystal after the dissociation of C-H complexes, subsequent diffusion and recombining again with carbon atom to reform C-H complexes.

scholarly journals A MATHEMATICAL THEORY FOR VIBRATIONAL LEVELS ASSOCIATED WITH HYDROGEN BONDS II: THE NON-SYMMETRIC CASE

2009 ◽  
Vol 21 (02) ◽  
pp. 279-313 ◽  
Author(s):  
GEORGE A. HAGEDORN ◽  
ALAIN JOYE
Keyword(s):  
Hydrogen Bonds ◽  
Arbitrary Order ◽  
Symmetric Case ◽  
Vibrational Modes ◽  
Electron Energy Level ◽  
Vibrational Levels ◽  
Oppenheimer Approximation ◽  
Electronic Motion ◽  
Specialized Form ◽  
The Masses

We propose an alternative to the usual time-independent Born–Oppenheimer approximation that is specifically designed to describe molecules with non-symmetrical hydrogen bonds. In our approach, the masses of the hydrogen nuclei are scaled differently from those of the heavier nuclei, and we employ a specialized form for the electron energy level surface. As a result, the different vibrational modes appear at different orders of approximation. Although we develop a general theory, our analysis is motivated by an examination of the FHCl- ion. We describe our results for it in detail. We prove the existence of quasimodes and quasienergies for the nuclear vibrational and rotational motion to arbitrary order in the Born–Oppenheimer parameter ∊. When the electronic motion is also included, we provide simple formulas for the quasienergies up to order ∊3 that compare well with experiment and numerical results.

scholarly journals New Light on UU Sagittae

1993 ◽  
Vol 155 ◽  
pp. 395-395
Author(s):  
S.A. Bell ◽  
D.L. Pollacco
Keyword(s):  
Planetary Nebula ◽  
Ultra Violet ◽  
Central Star ◽  
Primary Component ◽  
Emission Lines ◽  
Ccd Photometry ◽  
Medium Resolution ◽  
The Individual ◽  
The Masses ◽  
Absorption Features

New V and I band CCD photometry and medium resolution spectroscopy are used to derive the masses, luminosities and radii accurate to < 10% for the individual components of the eclipsing central star of the planetary nebula A63–UU Sge (M1 = 0.63 ± 0.06M⊙, R1 = 0.33 ± 0.01R⊙, M2 = 0.29 ± 0.04M⊙ and R2 = 0.53 ± 0.002R⊙). Emission lines from the secondary component and HeII and NV absorption features from the primary component are used to determine the first radial velocity curves of the system. Ultra–violet and optical spectra show that the temperature of the primary compoment is ∼ 105K – much larger than previously suspected. As the techniques used are essentially independent this is probably the most accurately known mass for a planetary nebula central star and therefore allows meaningful comparison to be made with evolutionary tracks for these objects.

Sign in / Sign up

Export Citation Format

Share Document