Symmetry of k·p Hamiltonian in pyramidal InAs/GaAs quantum dots: Application to the calculation of electronic structure

A method for the calculation of the electronic structure of pyramidal self-assembled InAs/GaAs quantum dots is presented. The method is based on exploiting the C-4 symmetry of the 8-band k·p Hamiltonian with the strain taken into account via the continuum mechanical model. The operators representing symmetry group elements were represented in the plane wave basis and the group projectors were used to find the symmetry adapted basis in which the corresponding Hamiltonian matrix is block diagonal with four blocks of approximately equal size. The quantum number of total quasiangular momentum is introduced and the states are classified according to its value. Selection rules for interaction with electromagnetic field in the dipole approximation are derived. The method was applied to calculate electron and hole quasibound states in a periodic array of vertically stacked pyramidal self-assembled InAs/GaAs quantum dots for different values of the distance between the dots and external axial magnetic field. As the distance between the dots in an array is varied, an interesting effect of simultaneous change of ground hole state symmetry, type, and the sign of miniband effective mass is predicted. This effect is explained in terms of the change of biaxial strain. It is also found that the magnetic field splitting of Kramer's double degenerate states is most prominent for the first and second excited state in the conduction band and that the magnetic field can both separate otherwise overlapping minibands and concatenate otherwise nonoverlapping minibands

Transport of F- ions in gaseous environment for technological applications

Negativni halogeni joni su zastupljeni u različitim neravnotežnim plazmama koje su zastupljene u biomedicinskim uređajima, nanotehnologijama, električnim pražnjenjima i hemiji atmosfere. Prikazani su podaci za modelovanje niskotemperaturnih plazmi koje sadrže F- jone primenom globalnih i drugih plazma modela. Ovaj jon je izabran zbog svoje izuzetno velike elektronegativnosti, veoma je jak nukleofilni reagent i formira veoma jake veze sa Luisovim kiselinama u gasnoj fazi. Sa druge strane, neizbežan je u proizvodnji c-BN filmova. Efikasni preseci za rasejanje F- jona na atomima Ar i molekulima F2, CF4 i BF3 dobijeni su primenom Nanbuove teorije u kojoj je moguće razdvojiti elastične od reaktivnih sudarnih procesa. Kako bi se uočili efekti nekonzervativnih sudarnih procesa na brzine drifta, proračuni su rađeni do visokih vrednosti E/N (1000Td).In this work we present swarm data obtained for F- ions in atomic and molecular gases necessary to form the global models for the complex collisional plasmas. We also present the new results for the simple scattering cross section set and proposed transport coefficients for F- ions in BF3 that can be used in such models. Nanbu’s theory based on thermodynamic threshold energies and separating elastic and reactive collisions is used to calculate cross sections for binary collisions of ions with atoms and molecules. For the cases in which the measured transport coefficients were available Momentum Transfer theory (MTT) was applied in order to unfold the cross sections from the measured transport data. Direct Monte Carlo method is applied to obtain swarm parameters at the temperature of T=300 K

Cross-Sections and Transport Properties of F- Ions in F-2

We present the new results for the simple scattering cross-section set and proposed transport coefficients for F- ions in F-2 that can be used in such models. Nanbu's theory based on thermodynamic threshold energies and separating elastic and reactive collisions is used to calculate cross-sections for binary collisions of ions with atoms and molecules. Direct MC method is applied to obtain swarm parameters at temperature of T = 300 K

Cross-Sections and Transport Properties of F- Ions in F-2

We present the new results for the simple scattering cross-section set and proposed transport coefficients for F- ions in F-2 that can be used in such models. Nanbu's theory based on thermodynamic threshold energies and separating elastic and reactive collisions is used to calculate cross-sections for binary collisions of ions with atoms and molecules. Direct MC method is applied to obtain swarm parameters at temperature of T = 300 K

Transport Parameters of F- Ions in BF3

In this work we presented the new results for energy dependent cross-sections and transport coefficients as a function of E/N for F- ions in BF3 gas. Results were obtained by using the Monte Carlo technique for cross-section set determined on the basis of the Nanbu theory. Monte Carlo method is applied to obtain swarm parameters at temperature of T = 300 K

Modeling of the effect of radicals on plasmas used for etching in microelectronics

Plazma nagrizanje predstavlja jedan od kritičnih koraka u izradi integrisanih kola. Dalja optimizacija plazma uređaja je potrebna jer nove generacije u tehnologiji zahtevaju različitu plazma hemiju. U ovom radu bavimo se uticajem radikala na plazma karakteristike, što je često zanemarivano u plazma modelima. Radikali dominiraju zahvatom elektrona čineći da je bazna smeša za nagrizanje slabo elektronegativna, a oni takođe modifikuju brzinu drifta preko modifikovanog balansa momenta. Mi smo koristili numerička rešenja Bolcmanove jednačine i Monte Karlo simulacije (MCS) za određivanje transportnih koeficijenata elektrona.Plasma etching represents one of the critical steps in manufacturing of integrated circuits. Further optimization of plasma equipment is needed since new generations in technology require different plasma chemistry. In this paper, we will study the influence of radicals on the plasma characteristics, since it was often neglected in plasma models. The radicals dominate attachment of electrons as the basic etching mixture is weakly electronegative and they also affect the drift velocity through modified momentum balance. We have used numerical solutions to the Boltzmann equation and Monte Carlo simulations (MCS) to determine the transport coefficients of electrons

Fleet renewal: An approach to achieve sustainable road transport

With more stringent requirements for efficient utilization of energy resources within the transport industry a need for implementation of sustainable development principles has appeared. Such action will be one of competitive advantages in the future. This is especially confirmed within the road transport sector. A methodology implemented in public procurement procedures for fleet renewal regarding the calculation of road vehicles’ operational lifecycle costs has been analyzed in detail in this paper. Afore mentioned calculation comprises the costs for: vehicle ownership, energy, carbon dioxide and pollutants emissions. Implementation of this methodology allows making the choice of energy efficient vehicles and vehicles with notable positive environmental effects. The objective of the research is to assess the influence of specific parameters of vehicle operational lifecycle costs, especially energy costs and estimated vehicle energy consumption, on vehicle choice in the procurement procedure. The case of urban bus fleet in Serbia was analyzed. Their operational lifecycle costs were calculated and differently powered vehicles were assessed. Energy consumption input values were defined. It was proved that defined fleet renewal scenarios could influence unquestionable decrease in energy consumption

Modeling of the effect of radicals on plasmas used for etching in microelectronics

Plazma nagrizanje predstavlja jedan od kritičnih koraka u izradi integrisanih kola. Dalja optimizacija plazma uređaja je potrebna jer nove generacije u tehnologiji zahtevaju različitu plazma hemiju. U ovom radu bavimo se uticajem radikala na plazma karakteristike, što je često zanemarivano u plazma modelima. Radikali dominiraju zahvatom elektrona čineći da je bazna smeša za nagrizanje slabo elektronegativna, a oni takođe modifikuju brzinu drifta preko modifikovanog balansa momenta. Mi smo koristili numerička rešenja Bolcmanove jednačine i Monte Karlo simulacije (MCS) za određivanje transportnih koeficijenata elektrona.Plasma etching represents one of the critical steps in manufacturing of integrated circuits. Further optimization of plasma equipment is needed since new generations in technology require different plasma chemistry. In this paper, we will study the influence of radicals on the plasma characteristics, since it was often neglected in plasma models. The radicals dominate attachment of electrons as the basic etching mixture is weakly electronegative and they also affect the drift velocity through modified momentum balance. We have used numerical solutions to the Boltzmann equation and Monte Carlo simulations (MCS) to determine the transport coefficients of electrons

Multicomponent Modelling Kinetics and Simultaneous Thermal Analysis of Apricot Kernel Shell Pyrolysis

Apricot kernel shells are naturally available source of biomass with potential for conversion to clean energy through a thermo-chemical process such as pyrolysis. To facilitate further process development, an advanced mathematical model which represents the process kinetics is developed and validated on the thermal decomposition studies using simultaneous thermal analysis, over a temperature range of 30-900 °C, at four heating rates of 5, 10, 15 and 20 °C min−1, under argon atmosphere. Model-free analysis and numerically developed methods were utilized for determination of effective activation energies, pre-exponential factors and the fractional contribution. A novel approach is introduced in order to determine actual pseudo-components of studied biomass that are included in its composition. The comparative study of the obtained kinetic results was also presented. The results obtained strongly indicated that the pseudo-component reaction modelling method could be employed to predict the experimental devolatilization rate and biomass composition with a high likelihood of success