Scaling properties of equilibrating semiconductor mounds of various initial shapes

A surface below its roughening temperature consisting of two dimensional concentric circular monoatomic steps is discussed under step-flow model. Entropic interactions between the steps are considered and the diffusion equation is solved in two dimensional polar coordinates. It is assumed that the local mass transfer occurs due to surface diffusion only during the evolution of the initial surface. The evolution of initial surfaces bounded by both a sinusoidal and other envelope functions of the form x? are considered. The evolution of the height of surface as a function of time is analyzed for each surface in Diffusion Limited (DL) regime. We have determined three scaling characteristics of evolution of the height of the surface. For an initial sinusoidal surface profile we have the following findings: The height of surface approximately decreases as ?? where ? is independent of wavelength and initial height of the surface. The time dependence of the evolution of the height scales with the cube of the wavelength of the initial surface. Finally the normalized height of the initial surfaces of different amplitudes with the same wavelength scales linearly with the amplitude as a function of time. Similar findings are obtained for non-sinusoidal initial surfaces also. © 201

Equilibration of a cone: KMC simulation results

We study the equilibration of an initial surface of conic shape that consists of concentric circular monolayers by Kinetic Monte Carlo (KMC) method. The kinetic processes of attachment and/or detachment of particles to/from steps, diffusion of particles on the surface, along a step or cluster edges are considered. The difference between an up hill and down hill motion of a particle at a step are taken into account through the Ehrlich-Schwoebel (ES) barrier. The height of the cone evolves as h(0) - h(t) ~ t 1/? where h(0) is the initial height of the surface and ? is approximately 2. The ES barrier slows down the equilibration of the surface but the time dependence remains as given above. The exponent ? depends neither on ES barrier nor on the temperature. The equilibration is found also to be independent of energy barrier to the motion of particles along the step edges. The number of particles in each layer except the top two circular layers is found to decrease as t 0.57. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2012

Equilibration of a cone: KMC simulation results

We study the equilibration of an initial surface of conic shape that consists of concentric circular monolayers by Kinetic Monte Carlo (KMC) method. The kinetic processes of attachment and/or detachment of particles to/from steps, diffusion of particles on the surface, along a step or cluster edges are considered. The difference between an up hill and down hill motion of a particle at a step are taken into account through the Ehrlich-Schwoebel (ES) barrier. The height of the cone evolves as h(0) − h(t) ~ t1/α where h(0) is the initial height of the surface and α is approximately 2. The ES barrier slows down the equilibration of the surface but the time dependence remains as given above. The exponent α depends neither on ES barrier nor on the temperature. The equilibration is found also to be independent of energy barrier to the motion of particles along the step edges. The number of particles in each layer except the top two circular layers is found to decrease as t0.57

Mobility of large clusters on a semiconductor surface: Kinetic Monte Carlo simulation results

The mobility of clusters on a semiconductor surface for various values of cluster size is studied as a function of temperature by kinetic Monte Carlo method. The cluster resides on the surface of a square grid. Kinetic processes such as the diffusion of single particles on the surface, their attachment and detachment to/from clusters, diffusion of particles along cluster edges are considered. The clusters considered in this study consist of 150-6000 atoms per cluster on average. A statistical probability of motion to each direction is assigned to each particle where a particle with four nearest neighbors is assumed to be immobile. The mobility of a cluster is found from the root mean square displacement of the center of mass of the cluster as a function of time. It is found that the diffusion coefficient of clusters goes as D = A(T)N? where N is the average number of particles in the cluster, A(T) is a temperature-dependent constant and ? is a parameter with a value of about -0.64 < ? < -0.75. The value of ? is found to be independent of cluster sizes and temperature values (170-220 K) considered in this study. As the diffusion along the perimeter of the cluster becomes prohibitive, the exponent approaches a value of -0.5. The diffusion coefficient is found to change by one order of magnitude as a function of cluster size. © 2016 Chinese Physical Society and IOP Publishing Ltd

The investigation of the morphology of a decaying conic mound in the presence of repulsive and attractive step interactions

A surface below its roughening temperature consisting of two dimensional concentric circular monoatomic steps is discussed under step-flow model. Both repulsive and attractive interactions between steps are considered where they vary as r-2 and r-1 respectively where r is the terrace width between steps. The diffusion equation is solved in two dimensional polar coordinates with the assumption that the local mass transfer occurs due to surface diffusion only during the evolution of the initial surface. The evolution of an initial surface which has a regular cone shape is considered. The morphology and the evolution of the height of surface as a function of time are analyzed in diffusion limited (DL) regime. While in the case of only repulsive interaction between steps surface evolves properly, when both repulsive and attractive interactions between steps are taken into account step bunchings separated by large flat terraces occur on the surface for some parameter values that depend on the relative strength of attractive and repulsive step interactions and the line tension of circular steps. A phase diagram separating the step bunching and no step bunching regions in parameter space is also obtained. © 2018 Elsevier B.V

The electronic structure of wurtzite MnS

National Nuclear Energy Agency of Indonesia (BATAN);Directorate Higher Edu. Ministry Natl. Edu. Indonesia (DIKTI);International Atomic Energy Agency (IAEA);International Union of Crystallography (IUCr);Abdus Salam International Centre for Theoretical Physics (ICTP);Deutsche Forschungsgemeinschaft (DFG)International Conference on Neutron and X-ray Scattering 2007, ICNX 2007 --23 July 2007 through 31 July 2007 -- Serpong and Bandung --Manganese sulfide thin films have been investigated by X-ray Absorption Fine Structure spectroscopy (XAFS). XAFS provides a description of the structure of the films. The paper also presents a structural characterisation of the wurtzite MnS thin films and their crystallisation behaviour by annealing at increasing temperatures. The x-ray absorption fine structure (XAFS) of Mn K-edge and S K-edge in wurtzite MnS have been investigated. The full multiple scattering approach has been applied to the calculation of Mn K edge XANES spectra of MnS. The calculations are based on different choices of one electron potentials according to Mn coordinations by using the real space multiple scattering method FEFF 8.0 code. The crystallographic and electronic structure of the MnS are tested at various temperature ranges from 300 to 573 K. We have found prominent changes in the XANES spectra of Mangeanese sulfide thin films by the change of the temperature. Such observed changes are explained by considering the structural, electronic and spectroscopic properties. The results are consistent with experimental spectra. © 2008 American Institute of Physics

Investigation of equilibration and growth of stepped surfaces by Kinetic Monte Carlo in one dimension

Turkish Physical Society 32nd International Physics Congress, TPS 2016 --6 September 2016 through 9 September 2016 -- --In this study, the equilibration and in the case of a particle flux to the surface, the growth of a one dimensional semi-conductor surface of "V" initial shape is investigated by kinetic Monte Carlo method. The initial surface is assumed to consist of atomic height steps separated by terraces. In Monte Carlo simulations, the following processes are considered: the diffusion of free particles on the surface, the attachment/detachment of particles to/from step edges from/to a terrace in front of a step or to a terrace above the step. In the simulations the Ehrlich-Schwoebel barrier is also taken into account. The equilibration of "V" initial shape at various temperatures is investigated. Moreover, the effect of particle bonding energy on the surface profile and on the evolution of the surface is also investigated. In the case of a particle flux to the surface, the surface profile and its growth kinetics are investigated at various temperatures and flux values. © 2017 Author(s)