Density-of-states effective mass and scattering parameter measurements by transport phenomena in thin films

2000 ◽  
Vol 71 (2) ◽  
pp. 462-466 ◽  
Author(s):  
D. L. Young ◽  
T. J. Coutts ◽  
V. I. Kaydanov
Keyword(s):  
Thin Films ◽  
Effective Mass ◽  
Density Of States ◽  
Transport Phenomena ◽  
Scattering Parameter

Structural, Optical, and Electron Transport Qualities of Zinc-Stannate Thin Films

2001 ◽  
Vol 666 ◽  
Author(s):  
David L. Young ◽  
Timothy J. Coutts ◽  
Don L. Williamson
Keyword(s):  
Thin Films ◽  
Effective Mass ◽  
Conduction Band ◽  
Fermi Energy ◽  
Impurity Scattering ◽  
Rf Magnetron Sputtering ◽  
Scattering Parameter ◽  
Band Theory ◽  
Zinc Stannate ◽  
Dependent Transport

ABSTRACTSingle-phase, spinel zinc stannate (ZTO = Zn2SnO4) thin films were grown by rf magnetron sputtering onto glass substrates. Uniaxially oriented films with resistivities of 10−2 -10−3 ωcm, mobilities of 16 - 26 cm2/V-s, and n-type carrier concentrations in the low 1019 cm−3 range were achieved. X-ray diffraction peak intensity studies established the films to be in the inverse spinel configuration. 119Sn Mössbauer studies identified two octahedral Sn sites, each with a unique quadrupole splitting, but with a common isomer shift consistent with Sn+4. A pronounced Burstein-Moss shift moved the optical bandgap from 3.35 eV to as high as 3.89 eV.Density-of-states effective mass, relaxation time, mobility, Fermi energy level, and a scattering parameter were calculated from transport data. Effective-mass values increased with carrier concentration from 0.16 to 0.26 me as the Fermi energy increased from 0.2 to 0.9 eV above the conduction-band minimum. First-order nonparabolic conduction-band theory was applied to extrapolate a bottom-of-the-band effective mass of 0.15 me. Calculated scattering parameters and temperature-dependent transport measurements correlated well with ionized impurity scattering with screening by free electrons for highly degenerate films.

Density-of-States Effective Mass and Scattering Parameter Measurements on Transparent Conducting Oxides Using Second-Order Transport Phenomena

2000 ◽  
Vol 623 ◽  
Author(s):  
D. L. Young ◽  
T. J. Coutts ◽  
X. Li ◽  
J. Keane ◽  
V. I. Kaydanov ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Effective Mass ◽  
Density Of States ◽  
Transport Theory ◽  
Transparent Conducting Oxides ◽  
Impurity Scattering ◽  
Scattering Mechanism ◽  
Scattering Parameter ◽  
Conducting Oxides ◽  
Transparent Conducting

AbstractTransparent conducting oxides (TCO) have relatively low mobilities, which limit their performance optically and electrically, and which limit the techniques that may be used to explore their band structure via the effective mass. We have used transport theory to directly measure the density-of-states effective mass and other fundamental electronic properties of TCO films. The Boltzmann transport equation may be solved to give analytic solutions to the resistivity, Hall, Seebeck, and Nernst coefficients. In turn, these may be solved simultaneously to give the density-of-states effective mass, the Fermi energy relative to either the conduction or valence band, and a scattering parameter, s, which characterizes the relaxation time dependence on the carrier energy and can serve as a signature of the dominate scattering mechanism. The little-known Nernst effect is essential for determining the scattering parameter and, thereby, the effective scattering mechanism(s). We constructed equipment to measure these four transport coefficients on the same sample over a temperature range of 30 – 350 K for thin films deposited on insulating substrates. We measured the resistivity, Hall, Seebeck, and Nernst coefficients for rf magnetron-sputtered aluminum-doped zinc oxide. We found that the effective mass for zinc oxide increases from a minimum value of 0.24me, up to a value of 0.47me, at a carrier density of 4.5 × 1020 cm−3, indicating a nonparabolic conduction energy band. In addition, our measured density-of-states effective values are nearly equal to conductivity effective mass values estimated from the plasma frequency, denoting a single energy minimum with a nearly spherical, constant-energy surface. The measured scattering parameter, mobility vs. temperature, along with Seebeck coefficient values, characterize ionized impurity scattering in the ZnO:AI and neutral impurity scattering in the undoped material.

scholarly journals Laser energy tuning of carrier effective mass and thermopower in epitaxial oxide thin films

2012 ◽  
Vol 100 (16) ◽  
pp. 162106 ◽  
Author(s):  
A. I. Abutaha ◽  
S. R. Sarath Kumar ◽  
H. N. Alshareef
Keyword(s):  
Thin Films ◽  
Effective Mass ◽  
Laser Energy ◽  
Oxide Thin Films ◽  
Carrier Effective Mass ◽  
Epitaxial Oxide ◽  
Energy Tuning

scholarly journals Effect of band structure adjustment based of Cu site on the thermoelectric properties of BiCuSeO

2021 ◽  
Author(s):  
Bo Feng
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Effective Mass ◽  
Valence Band ◽  
Thermoelectric Properties ◽  
Density Of States ◽  
First Principles Calculation ◽  
Temperature Range ◽  
Ti Doping

Abstract The effect of Ti doped at Cu site on the thermoelectric properties of BiCuSeO was studied by experimental method and first principles calculation. The results show that Ti doping can cause the lattice contraction and decrease the lattice constant. Ti doping can increase the band gap and lengthen the Cu/Ti-Se bond, resulting in the decrease of carrier concentration. Ti doping can reduce the effective mass and the Bi-Se bond length, correspondingly improve the carrier mobility. Ti doping can decrease the density of states of Cu-3d and Se-4p orbitals at the top of valence band, but Ti-4p orbitals can obviously increase the density of states at the top of valence band and finally increase the electrical conductivity in the whole temperature range. With the decrease of effective mass, Ti doping would reduce the Seebeck coefficient, but the gain effect caused by the increase of electrical conductivity is more than the benefit reduction effect caused by the decrease of Seebeck coefficient, and the power factor shows an upward trend. Ti doping can reduce Young's modulus, lead to the increase of defect scattering and strain field, correspondingly reduce the lattice thermal conductivity and total thermal conductivity. It is greatly increased for the ZT values in the middle and high temperature range, with the highest value of 1.04 at 873 K.

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