Study on formation of step bunching on 6H-SiC (0001) surface by kinetic Monte Carlo method

Li, Yuan; Chen, Xuejiang; Su, Juan

doi:10.1016/j.apsusc.2016.02.237

Cited by 22 publications

(10 citation statements)

References 32 publications

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“…Crystals with thicknesses near 40 μm had more than ten times the number of steps per unit of crystal length (~20 steps/10 μm) than the thinnest crystals with thicknesses of just a few μm (~1 step/10 μm). Such variations in step density with crystal thickness are commonly observed in a variety of materials and reflect changes in step flow growth kinetics with temperature and vapor flux 30 – 32 . As expected, the step heights were 1.8 nm, corresponding to the c -axis dimension of the triclinic Cl 2 -NDI unit cell, i.e., the thickness of one Cl 2 -NDI layer.…”

Section: Resultsmentioning

confidence: 93%

Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors

D’Avino

et al. 2018

Nat Commun

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Understanding relationships between microstructure and electrical transport is an important goal for the materials science of organic semiconductors. Combining high-resolution surface potential mapping by scanning Kelvin probe microscopy (SKPM) with systematic field effect transport measurements, we show that step edges can trap electrons on the surfaces of single crystal organic semiconductors. n-type organic semiconductor crystals exhibiting positive step edge surface potentials display threshold voltages that increase and carrier mobilities that decrease with increasing step density, characteristic of trapping, whereas crystals that do not have positive step edge surface potentials do not have strongly step density dependent transport. A device model and microelectrostatics calculations suggest that trapping can be intrinsic to step edges for crystals of molecules with polar substituents. The results provide a unique example of a specific microstructure–charge trapping relationship and highlight the utility of surface potential imaging in combination with transport measurements as a productive strategy for uncovering microscopic structure–property relationships in organic semiconductors.

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Section: Resultsmentioning

confidence: 93%

Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors

D’Avino

et al. 2018

Nat Commun

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“…To understand the behavior of the terrace fraction at steady-state and as a function of time after a change in growth rate, we have developed a model based on BCF theory for vicinal surfaces with a sequence of steps 2 . This type of one-dimensional model considers adatom diffusion on terraces with boundary conditions at the steps defining the terrace edges, and has been used extensively to understand the step-bunching instability [45][46][47][48][49][50] , step pairing 51 , step width fluctuations 52 , growth mode transitions 53 , and competitive adsorption 54 . Typically, all steps in a sequence are assumed have identical properties.…”

Section: Burton-cabrera-frank Theory For Vicinal C-plane Surfacesmentioning

confidence: 99%

“…The solutions are the same as Eqs. (46)(47)(48)(49), with p j , q j , and ρ j eq replaced by pj , qj , and ρj eq , respectively. Unfortunately, since the ρj eq that appear in the C 1i and C 2i depend upon the step velocities v j , which in turn depend upon the C 1i and C 2i via Eqs.…”

Section: Analytical Solution For Transparent Stepsmentioning

confidence: 99%

“…We start with Eqs. (46)(47)(48)(49), with p j , q j , and ρ j eq replaced by pj , qj , and ρj eq , respectively. In the limit where the diffusion length within an adatom lifetime is much larger than the terrace widths, √ Dτ >> w, the coefficients c i can be set equal to unity, and the coefficients s i are small quantities given by s i = w i /(2 √ Dτ ).…”

Section: E Simplified Analytical Solutionmentioning

confidence: 99%

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Dynamics of Atomic Steps on GaN (0001) during Vapor Phase Epitaxy

Ju,

Xu,

Thompson

et al. 2020

Preprint

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Images of the morphology of GaN (0001) surfaces often show half-unit-cell-height steps separating a sequence of terraces having alternating large and small widths. This can be explained by the αβαβ stacking sequence of the wurtzite crystal structure, which results in steps with alternating A and B edge structures for the lowest energy step azimuths, i.e. steps normal to [0110] type directions. Predicted differences in the adatom attachment kinetics at A and B steps would lead to alternating α and β terrace widths. However, because of the difficulty of experimentally identifying which step is A or B, it has not been possible to determine the absolute difference in their behavior, e.g. which step has higher adatom attachment rate constants. Here we show that surface X-ray scattering can measure the fraction of α and β terraces, and thus unambiguously differentiate the growth dynamics of A and B steps. We first present calculations of the intensity profiles of GaN crystal truncation rods (CTRs) that demonstrate a marked dependence on the α terrace fraction fα. We then present surface X-ray scattering measurements performed in situ during homoepitaxial growth on (0001) GaN by vapor phase epitaxy. By analyzing the shapes of the (101L) and (011L) CTRs, we determine that the steady-state fα increases at higher growth rate, indicating that attachment rate constants are higher at A steps than at B steps. We also observe the dynamics of fα after growth conditions are changed. The results are analyzed using a Burton-Cabrera-Frank model for a surface with alternating step types, to extract values for the kinetic parameters of A and B steps. These are compared with predictions for GaN (0001).

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“…to model the meandering of curved steps [5][6][7][8][9] , the simple case of onedimensional diffusion between relatively straight steps on vicinal surfaces is also very powerful. One-dimensional BCF models have been used extensively to understand the step-bunching instability [10][11][12][13][14][15][16] , step pairing 17,18 , step width fluctuations 4 , growth mode transitions 19 , and competitive adsorption 20 .…”

Section: Introductionmentioning

confidence: 99%

Burton-Cabrera-Frank theory for surfaces with alternating step types

Ju,

Xu,

Thompson

et al. 2020

Preprint

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Burton-Cabrera-Frank (BCF) theory has proven to be a versatile analysis to relate surface morphology and dynamics during crystal growth to the underlying mechanisms of adatom diffusion and attachment at steps. For an important class of crystal surfaces, including the basal planes of hexagonal close-packed and related systems, the steps in a sequence on a vicinal surface can exhibit properties that alternate from step to step. Here we develop BCF theory for such surfaces, to relate observables such as the alternating terrace widths as a function of growth conditions to the kinetic coefficients for adatom attachment at steps. We include the effects of step transparency and step-step repulsion. A general solution is obtained for the dynamics of the terrace widths assuming quasi-steady-state adatom distributions on the terraces, and an explicit simplified analytical solution is obtained under widely applicable approximations. We obtain expressions for the steady-state terrace fractions as a function of growth rate. Limiting cases of diffusion-limited, attachment-limited, and mixed kinetics are considered.

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Study on formation of step bunching on 6H-SiC (0001) surface by kinetic Monte Carlo method

Cited by 22 publications

References 32 publications

Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors

Crystal step edges can trap electrons on the surfaces of n-type organic semiconductors

Dynamics of Atomic Steps on GaN (0001) during Vapor Phase Epitaxy

Burton-Cabrera-Frank theory for surfaces with alternating step types

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