Bulk modulus semiconductors

Results for semiconductors may depend upon the chosen pseudopotential[115, 112,110,116]. Table 9 summarizes some results, listing them by how the pseudopotential for the core electrons was constructed, and how the valence electrons were treated. The considerable variation in these results suggests that more all-electron calculations may be needed to decide this issue. Trends suggest that, in going from LSD to GGA, the lattice constant, a, goes from underestimated to overestimated, the cohesive energy, Ecoh, is improved, but the bulk modulus, B, is worsened. 

The Debye characteristic temperature of isotropic bodies is directly associated with the bulk modulus and therefore with all the other properties of matter dependent, to a certain degree, on the atomization energy, the surface energy u, the elasticity moduli, the expansion coefficients, the width of the forbidden band in semiconductors, etc. 

The less energy gap for the semiconductor compounds the less is bulk modulus and the larger mean-square amplitude. 

The bulk modulus decreases and mean-square vibration amplitude increases when going from GaP to InSb. The band gap Eg decreases at the same time. We see that the strength of the interatomic bonding reduces with increasing the sum Ha + Hs, where Ha and wb are the principal quantum numbers of the outer shells for the a " and elements, respectively. The sum jia + ub equals for C, Si, and Ge to 4, 6, and 8, respectively. It changes from 7 for the semiconductor GaP to 9 for InSb. 

Al-Douri Y, Abid H, Aourag H (2005) Correlation between the bulk modulus and the transition pressure in semiconductors. Mater Lett 59 2032-2034... 

In summary we can show, in a qualitative way, the transition of valency from divalent over intermediate valent towards trivalency by plotting the bulk modulus as function of pressure as shown in fig. 99. The different regions (semiconductor, intermediate-valent semiconductor, intermediate-valent metal, metal) are clearly indicated (Boppart and Wachter 1984c). 

Bulk elastic modulus, of binary compound semiconductors, 22 145, 146-147t Bulk enzymes, from genetically engineered microbes, 22 480 Bulk erosion, 9 78 Bulk fluid velocity method, 16 688 Bulk gallium nitride, supercritical ammonia solution growth of, 14 96-97 Bulk gases... 

The technological importance of thin films in such areas as semiconductor devices and sensors has led to a demand for mechanical property information for these systems. Measuring the elastic modulus for thin films is much harder than the corresponding measurement for bulk samples, since the results obtained by traditional indentation methods are strongly perturbed by the properties of the substrate material. Additionally, the behaviour of the film under conditions of low load, which is necessary for the measurement of thin-film properties, is strongly influenced by surface forces [75]. Since the force microscope is both sensitive to surface forces and has extremely high depth resolution, it shows considerable promise as a technique for the mechanical characterization of thin films. 

Theoretical studies suggest [32] that BN nanotubes should be semiconductors with a band gap of 5.5 eV lower than in bulk BN. This property is independent of tube diameter, chirality and the number of walls. However, recent ab intio calculations show that under polygonisation, BN nanotubes reduce their band gap to ca. 1.5 - 2 eV [ 168]. They also appear to be resistant to oxidation and may therefore find use in materials science. In fact, experimental determination of the Young s modulus in BN tubes (Y = 1.22 0.24 TPa) [169] confirms various theoretical elastic calculations on nanotubes [170-172] and reveals that BN tubes are highly crystalline and maybe the strongest insulating nanofibres [169,170]. 

---