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First-principle calculations of effective mass of silicon crystal with vacancy defects

Zhong S., Wu M., Lei X.

Materials Science Poland

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2016

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Vol. 34, No. 4

916--923

EN

The energy band structures and electron (hole) effective masses of perfect crystalline silicon and silicon with various vacancy defects are investigated by using the plane-wave pseudopotential method based on density functional theory. Our results show that the effect of monovacancy and divacancy on the energy band structure of crystalline silicon is primarily reflected in producing the gap states and the local states in valence band maximum. It also causes breaking the symmetry of energy bands resulting from the Jahn-Teller effect, while only producing the gap states for the crystalline silicon with hexavacancy ring. However, vacancy point defects could not essentially affect the effective masses that are derived from the native energy bands of crystalline silicon, except for the production of defect states. Simultaneously, the Jahn-Teller distortions only affect the gap states and the local states in valence band maximum, but do not change the symmetry of conduction band minimum and the nonlocal states in valence band maximum, thus the symmetry of the effective masses. In addition, we study the electron (hole) effective masses for the gap states and the local states in valence band maximum.

2

Siły wiązania metalicznego między płaszczyznami grafenowymi w graficie

Rozpłoch F., Patyk J., Stankowski J., Szroeder P.

Karbo

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2008

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Nr 1

9-12

PL

W celu ukazania metalicznego charakteru sił wiążących dwuwymiarową sieć grafenu w trójwymiarowy grafit porównano właściwości fizyczne grafitu, metali oraz kryształów molekularnych. Zarówno obliczenia tearetyczne Santosa i Villagry, jak również dane eksperymentalne dotyczące przewodnictwa elektrycznego oraz cieplnego dostarczają argumentów wskazujących na niezwiązane elektrony π, jako źródło występowania słabych sił między warstwami. Oddziaływania między warstwami są określone przez niską koncentrację elektronów quasi-swobodnych elektronów oraz stosunkowo małą masę efektywną.

EN

Physical properties of graphite, metals and molecular crystals are compared to show metallic character of forces bonding 2-D graphene layers into 3-D graphite. Both theoretical calculations performed by Santos and Villagra as well such experimental data as electrical and thermal conductivity deliver strong arguments for itinerant π-electrons to be responsible for existence of weak interlayer attractive forces. The intensity of interlayer interaction is determined by small concentration of itinerant electrons and comparatively small effective mass.

3

Characteristics of quantum beats in InGaN/GaN quantum well

Gao F., Xiong G.

Optica Applicata

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2005

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Vol. 35, nr 4

919-926

EN

A L-type three level atom in the InGaN/GaN quantum wells is formed by the lowest energy level of conductive electrons and the highest sub-bands of light and heavy hole. With the excitation of the coherent light field, a quantum beat spectrum is obtained. The quantum beat spectrum can be calculated by using the theory of effective mass. Quantum beats do not exist in all polarization directions. The influence of quantum well width and the concentration of In on the spectra of quantum beats is also discussed.

4

Electron-electron correlations in (BEDT-TTF)2I3 organic superconductors

Balthes E., Nothardt A., Wyder P., Schweitzer D.

Materials Science Poland

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2004

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Vol. 22, No. 4

285--298

EN

The detection of the fractional Landau level filling factor a?= 1/2 and low integer filling factors in the two-dimensional multilayer organic metal a-(BED-TTF)2I3 is presented, which shows the occurrence of electron localisation and electron-electron correlation in this bulk metallic two-dimensional system. These effects are found in the normal conducting state of the organic superconductor a-(BEDT-TTF)2I3. In addition, quantum oscillation measurements are found to be a very promising tool for direct detection of the chemical potential and its variation with magnetic field, even under rather complex fermiological conditions.