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Articles 1 - 6 of 6
Full-Text Articles in Physics
Heat Transport In Sb2àXvxte3 Single Crystals, Jeffrey Dyck, W. Chen, C. Uher, Č. DrašAr, P. LošŤÁK
Heat Transport In Sb2àXvxte3 Single Crystals, Jeffrey Dyck, W. Chen, C. Uher, Č. DrašAr, P. LošŤÁK
Jeffrey Dyck
Antimony telluride doped with small concentrations of vanadium was recently identified as a diluted magnetic semiconductor. We present a study of the heat transport in single crystals of [formula] with [formula] 0.01, 0.02, and 0.03. Thermopower and thermal conductivity were measured from 1.5 K to 300 K. The thermopower is positive for all samples investigated and has a modest dependence on vanadium content. At low temperatures, the lattice thermal conductivity has an approximate [formula] dependence and the data up to 100 K can be fitted well assuming that phonons scatter on boundaries, point defects, charge carriers, and other phonons. Theoretical …
The Role Of Bandgap In The Secondary Electron Emission Of Small Bandgap Semiconductors: Studies Of Graphitic Carbon, Neal E. Nickles
The Role Of Bandgap In The Secondary Electron Emission Of Small Bandgap Semiconductors: Studies Of Graphitic Carbon, Neal E. Nickles
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The question of whether the small bandgaps of semiconductors play a significant role in their secondary electron emission properties is investigated by studying evaporated graphitic amorphous carbon, which has a roughly 0.5 eV bandgap, in comparison with microcrystalline graphite, which has zero bandgap. The graphitic amorphous carbon is found to have a 30% increase in its maximum secondary electron yield over that of two microcrystalline graphite samples with comparable secondary electron yields: highly oriented pyrolytic graphite and colloidal graphite. The potentially confounding influence of the vacuum level has been isolated through the measurement of the photoelectron onset energy of the …
Transport Properties Of Polycrystalline Type-I Sn Clathrates, G. S. Nolas, J. L. Cohn, Jeffrey Dyck, C. Uher, J. Lang
Transport Properties Of Polycrystalline Type-I Sn Clathrates, G. S. Nolas, J. L. Cohn, Jeffrey Dyck, C. Uher, J. Lang
Jeffrey Dyck
Thermal conductivity, resistivity, Seebeck coefficient, and Hall measurements on polycrystalline Sn-clathrate compounds with the type-I hydrate crystal structure are reported. Interstitial alkali-metal atoms in these compounds reside inside polyhedral cavities formed by the tetrahedrally bonded Sn network atoms. Localized disorder associated with “rattling” motion of these interstitial atoms contributes to the low thermal conductivity of these semiconducting compounds. The Hall coefficient and resistivity for some compounds exhibit nonmonotonic temperature dependences consistent with a crossover with decreasing temperature from conduction-band to impurity-band conduction. The carrier mobility is found to be low even in the absence of interstitial atoms within the Sn …
Diluted Magnetic Semiconductors Based On Sb2àXvxte3 „0.01ïXï0.03., Jeffrey Dyck, Pavel Hájek, Petr LošŤÁK, Ctirad Uher
Diluted Magnetic Semiconductors Based On Sb2àXvxte3 „0.01ïXï0.03., Jeffrey Dyck, Pavel Hájek, Petr LošŤÁK, Ctirad Uher
Jeffrey Dyck
We report on a diluted magnetic semiconductor based on the [formula] tetradymite structure doped with very low concentrations of vanadium (1—3 at. %). The anomalous transport behavior and robust magnetic hysteresis loops observed in magnetotransport and magnetic measurements are experimental manifestations of the ferromagnetic state in these materials. The [formula] exchange between holes and vanadium [formula] spins is estimated from the behavior of the magnetoresistance. A Curie temperature of at least 22 K is observed for [formula] This discovery offers possibilities for exploring magnetic properties of other tetradymite structure semiconductors doped with a wide range of [formula] transition metals.
Effect Of Ni On The Transport And Magnetic Properties Of Co1àXnixsb3, Jeffrey Dyck, Wei Chen, Jihui Yang, Gregory P. Meisner, Ctirad Uher
Effect Of Ni On The Transport And Magnetic Properties Of Co1àXnixsb3, Jeffrey Dyck, Wei Chen, Jihui Yang, Gregory P. Meisner, Ctirad Uher
Jeffrey Dyck
The filled skutterudite compounds based on the binary skutterudite [formula] are currently being investigated for their potential applications as thermoelectric materials. One route to optimization of these compounds is by doping on the Co site. An obvious candidate for an n-type dopant is Ni, since it has one more electron in its valence shell than Co. Up to now, however, only high concentrations of Ni in [formula] have been studied; and the valence of Ni in this compound and its influence on the transport and magnetic properties has been an open question. We present electrical resistivity, thermopower, Hall effect, magnetoresistance, …
Dispersion Analysis Of Sns And Snse, Haluk Şafak, Mustafa Merdan, Ö. Faruk Yüksel
Dispersion Analysis Of Sns And Snse, Haluk Şafak, Mustafa Merdan, Ö. Faruk Yüksel
Turkish Journal of Physics
The reflectance spectra of single crystals of SnS and SnSe were measured at normal incidence by unpolarized light. The refractive indices of speciemens were calculated by Kramers-Kronig Analysis. On the basis of the Wemple diDomenico single oscillator model, the dispersion parameters were determined. It is found that the parameters obtained by unpolarized light are, in general close to those reported for polarized cases. Morever, a close similarity were observed with E//b polarization for SnS.