Untitled

Nakahata, Seiji; Sogabe, Kouichi; Matsuura, Takahiro; Yamakawa, Akira

doi:10.1023/a:1018513108753

Cited by 9 publications

(3 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2(b). A similar relationship was observed in as-sintered AlN ceramics with Y 2 O 3 additives by Nakahata et al 11) They reported that the density of unpaired electrons responsible for a signal at g ¼ 2:007 increases with an increase in thermal conductivity in the range of 174 -258 W m À1 K À1 . 6) The linewidths of both signals were also very similar.…”

Section: Relationship With Thermal Conductivitysupporting

confidence: 80%

“…9,10) In general considerations, defects in the lattice lower the thermal conductivity, as described above. However, Nakahata et al 11) found that the thermal conductivity increases with increasing concentration of defects responsible for the ESR signal at g ¼ 2:007 in as-sintered Y 2 O 3added AlN ceramics. They assigned the g ¼ 2:007 ESR signal to electrons trapped by V N (F-center) and suggested that the concentration of V N centers is inversely related to the concentration of O N centers.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electron Spin Resonance of Defects Related to Thermal Conductivity in AlN Ceramics

Kai

Tomohiro

Kanechika

et al. 2008

jjap

View full text Add to dashboard Cite

Defects of AlN ceramics with a thermal conductivity from 102 to 216 W m À1 K À1 are investigated using electron spin resonance (ESR). Two ESR signals at g ¼ 2:006 and 1.999 are related to thermal conductivity. The g ¼ 1:999 signal intensity increases with a decrease in thermal conductivity, an increase in oxygen concentration, and an increase in Mg concentration. The g ¼ 1:999 signal is tentatively supposed to be caused by an electron-trapped center. The g ¼ 2:006 signal intensity is increased with an increase in thermal conductivity, a decrease in oxygen concentration, and an increase in Ca concentration. A defect responsible for the g ¼ 2:006 signal is assigned as a hole trapped in an O N -V Al complex.

show abstract

Section: Relationship With Thermal Conductivitysupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Electron Spin Resonance of Defects Related to Thermal Conductivity in AlN Ceramics

Kai

Tomohiro

Kanechika

et al. 2008

jjap

View full text Add to dashboard Cite

show abstract

“…It is interesting to note that using a defect equilibrium formulation, an expression can be derived showing that the concentration of oxygen is inversely related to the concentration of nitrogen vacancies. 55 Based on the growth procedure (SiC-seeded technique), the presence of vacancies and native defects in crystals #A and #B should be somewhat higher than in #C and #D (self-seeded growth and AlN-seeded techniques). However, this could not be resolved unambiguously by the present study.…”

Section: Optical Investigations On Aln Single Crystals: Results mentioning

confidence: 99%

The growth and optical properties of large, high-quality AlN single crystals

Straßburg

Senawiratne

Dietz

et al. 2004

Journal of Applied Physics

View full text Add to dashboard Cite

The effect of impurities and defects on the optical properties of AlN was investigated. High-quality AlN single crystals of more than 20mm2 size were examined. Different crucible materials and growth procedures were applied to the growth of bulk AlN by physical vapor transport method to vary the defect and the impurity concentrations. The crystalline orientation was investigated by Raman spectroscopy. Glow discharge mass spectrometry was used to determine the trace concentration of the incorporated impurities such as oxygen and carbon. The photoluminescence emission and absorption properties of the crystals revealed bands around 3.5 and 4.3eV at room temperature. Absorption edges ranging between 4.1 and 5.95eV were observed. Since no straight correlation of the oxygen concentration was obtained, a major contribution of oxygen or oxygen-related impurities was ruled out to generate the observed emission and absorption bands in the Ultraviolet spectral range. The carbon-related impurities and intrinsic defects might contribute to the observed optical properties. The absorption coefficient for AlN single crystals has been derived for the spectral range below the band edge.

show abstract

Compound Particle Swarm Optimization in Dynamic Environments

Liu

Wang

Yang

2008

Lecture Notes in Computer Science

View full text Add to dashboard Cite

Abstract. Adaptation to dynamic optimization problems is currently receiving a growing interest as one of the most important applications of evolutionary algorithms. In this paper, a compound particle swarm optimization (CPSO) is proposed as a new variant of particle swarm optimization to enhance its performance in dynamic environments. Within CPSO, compound particles are constructed as a novel type of particles in the search space and their motions are integrated into the swarm. A special reflection scheme is introduced in order to explore the search space more comprehensively. Furthermore, some information preserving and anti-convergence strategies are also developed to improve the performance of CPSO in a new environment. An experimental study shows the efficiency of CPSO in dynamic environments.

show abstract

Untitled

Cited by 9 publications

References 2 publications

Electron Spin Resonance of Defects Related to Thermal Conductivity in AlN Ceramics

Electron Spin Resonance of Defects Related to Thermal Conductivity in AlN Ceramics

The growth and optical properties of large, high-quality AlN single crystals

Compound Particle Swarm Optimization in Dynamic Environments

Contact Info

Product

Resources

About