Surface Miscut Research Articles

Observation of double- to single-domain transition on the Eu/Si(1 0 0) surface by LEED and STM

The orientational phase diagram and morphology of the Eu-adsorbed Si(1 0 0) surface miscut by 0.4° have been studied by low-energy electron diffraction and scanning tunneling microscopy. We demonstrate that the original double-domain configuration with single-layer steps on the Si(1 0 0) substrate can be drastically broken at 0.4 monolayer (ML) of Eu. At this coverage, the ordered domain pattern formed by topographically non-equivalent terraces with Eu-induced 2 × 3 and “2 × 1” (so-called “wavy” structure) reconstructions is found, while no orthogonal 3 × 2 and “1 × 2” domains are observed. A model of the single-domain surface is proposed. The origin of the double- to single-domain transition found for the Eu/Si(1 0 0) system is discussed.

Influence of Si deposition on the electromigration induced step bunching instability on Si(1 1 1)

Effects of Si deposition on electromigration induced step bunching on the Si(1 1 1)-(1 × 1) surface were studied for “temperature Regimes” I (∼850–950 °C) and II (∼1040–1190 °C) on “dimpled samples” that have a range of initial surface miscut angles (±0.5°). We find that a step-down electric current is required to induce bunching under both net sublimation and depositions conditions in temperature Regime I, in agreement with previous reports. However, for temperature “Regime II” we observe that step-up current is required to induce step bunching for both net deposition and net sublimation conditions, in contradiction with the report of Métois and Stoyanov [Surf. Sci. 440 (1999) 407] and suggested “step permeability” model of Stoyanov [Surf. Sci. 416 (1998) 200]. We further observe a strong reduction in the number of crossing steps on the wide terraces for near equilibrium Si flux conditions. We also report a systematic, nearly linear dependence of the step bunching rate on the initial sample miscut angle in both Regimes I and II, which is independent of net deposition/sublimation conditions.

Computer Simulation of the Surface Free Energy of the Si(100) Surface and the Line Free Energies Associated with Steps on This Surface

Many atomic-level 0 K thermodynamic properties of silicon (100) surfaces have been calculated from classical potential energy surfaces or from quantum ground-state Born−Oppenheimer surfaces. We present an easy and accurate computer simulation method for determining surface thermodynamic properties at high temperatures where the dynamics may be described classically. The method is illustrated with calculations of the surface free energies of the 2 × 1 and c(2 × 2) reconstructed (100) surfaces at T = 1000 K using the Stillinger−Weber interaction model for silicon. We then use an extension of our simulation method to determine the line free energies associated with steps. Enough examples of line free energies are given to enable us to calculate the equilibrium concentration of single and double steps as a function of the surface miscut angle. We also deduce the activation free energy associated with the Si adatom hopping over simple steps.

Preparation of the atomically straight step-edge Si (111) substrates as templates for nanostructure formation

ABSTRACTWe report on the experimental discovery that the distribution of kinks along steps on vicinal Si(111) surfaces depends on the direction of the dc current passed along the steps for resistive annealing. The as-cleaned Si(111) surface miscut ∼1° towards [112] has a small (<3°) unavoidable azimuthal deviation, which produces a number of kinks along the step-edges. When the azimuthal misorientation is from [112] towards [110] [110], dc current flowing in the direction [110] [110] climbing up the kinks straightens the step-edges as opposed to the current flowing in the opposite [110] [110]direction. During annealing around 800°C, the dc current in the direction climbing up the kinks straightens the steps. The up-climbing current direction transports and concentrates the kinks in a region outside the template area, leaving a kink-free atomic step-edge region as an ideal template for a variety of nanostructure formations. The straight step edges produced in this manner have uniform atomic configuration known as U(2, 0).

Two series of triple- and single-domain reconstructions induced by europium on vicinal Si(1 1 1) [ [formula omitted]]-miscut surface

The growth and properties of Eu-induced one-dimensional reconstructions on vicinal Si(1 1 1) surface miscut in the [ 1 ̄ 1 ̄ 2 ] direction have been studied by low energy electron diffraction and scanning tunneling microscope in the submonolayer range. The focus has been attended to the formation of single-domain structures and the influence of preparation parameters on the domain orientation. We have found the critical conditions for the preparation of a variety of Eu-induced single-domain ( n×2) and ( n×1) structures. In addition, a new intermediate phase showing the 9×1 periodicity between 3×2 and 2×1 phases is detected.

Tunable magnetization reversal in epitaxial bcc Fe1−xCox films on vicinal surfaces

The magnetic reversal of bcc Fe1−xCox thin films on vicinal Sc1−yEryAs/GaAs(100) is modified by changing the relative strength of the uniaxial and cubic magnetocrystalline anisotropies using substrates with different miscut angles. The surface miscut and applied field geometry are used to induce several changes in the reversal process, which includes up to three first-order jumps. Increasing the miscut angle of the substrate converts one of the easy axes of the cubic anisotropy into a hard axis. When the anisotropy has a local maximum, the first jump in the reversal process occurs at positive magnetic fields. As the angle between the in-plane magnetic field and the hard axis increases, this jump crosses over to continuous rotation. Two-component magneto-optical Kerr effect measurements are used to map out the hysteresis loops, and both components of the magnetization agree qualitatively with the results of a simple coherent rotation model.

Formation and thermal-desorption-controlled patterning of Yb-induced structures on vicinal Si( [formula omitted]) [ [formula omitted]]-miscut surface

Ytterbium-induced 3 × 2 and 5 × 1 reconstructions produced in submonolayer regime on stepped Si(1 1 1) surface miscut in the [ 1 ̄ 1 ̄ 2] direction are studied by scanning tunneling microscope and low-energy electron diffraction. The triple-domain structure is found for the 5 × 1 reconstruction. In contrast, the 3 × 2 reconstruction, formed by evaporating part of the Yb atoms from the 5 × 1 phase, exhibits the single-domain structure. Furthermore, the controlled patterning of the 3 × 2 phase, and the preparation of very straight 7 × 7-Si (or 5 × 5-Si) and 3 × 2-Yb stripes by thermal desorption of Yb atoms from Yb/Si interface are reported.

Periodic States in the Constrained Equilibrium of Vicinal Nb (011) Miscut along [100

At a temperature of 1700 K the Nb (011) vicinal surface miscut along $[100]$ is observed by low energy electron microscopy to be almost ideal, with single step edges of unit height. Below 1560 K, step edges coalesce to form a surface entirely of ${110}$ facets. In between these temperatures we observe states in which facets and dissociated steps alternate, to form periodic structures. For a simplified model these states form a stable phase in the constrained equilibrium of the vicinal surface.

Periodic faceting of a Si(113) surface miscut towards [110

The equilibrium morphology of a Si(113) surface miscut by a polar angle of 1.8° away from the (113) orientation along an azimuth within 3.5° of the [11̄0] direction has been characterized by X-ray scattering, for temperatures between 900 and 1450K. Above 1215K, a uniformly stepped surface is found. Between 1075 and 1215K, the surface phase-separates into two coexisting phases of different polar and azimuthal orientations. With decreasing temperature, the phase with the smaller polar angle approaches the (113) orientation, while the other phase exhibits an increasingly large polar angle (up to 9°). The two coexisting phases form a periodic groove structure with periodicity ranging from 740 to 940Å, depending on the temperature. Below 1075K, the phase with the larger polar angle further phase-separates into two phases of different azimuth (±17°), resulting in coexistence among three distinct phases. The three coexisting phases form a quasi-periodic array of pyramids.

Step Fluctuations on Vicinal Si(113)

The fluctuation properties of steps relevant to step coalescence have been measured using scanning tunneling microscopy on a Si(113) surface miscut along a low symmetry azimuth. In local thermal equilibrium at $710\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, coexistence of single, double, triple, and quadruple steps has been observed. From direct measurement of the step-correlation function, the step stiffness is shown to be proportional to the step height, with an additional stabilization of double-height steps. This result is shown to require a step-step attraction energy close to $\mathrm{kT}$.

Magnetization on Vicinal Ferromagnetic Surfaces

ABSTRACTUsing Ising model Monte Carlo simulations, we show a strong dependence of surface magnetization on surface miscut angle. For ferromagnetic surfaces, when surface spin exchange coupling is larger than that of the bulk, the surface magnetic ordering temperature decreases, toward the bulk Curie temperature, with increasing miscut angle; when surface spin exchange coupling is smaller than that of the bulk, a crossover behavior occurs: at low temperature, the surface magnetization decreases with increasing miscut angle; at high temperature, the reverse is true.

Diffraction of neutron standing waves in thin films

Diffraction of neutron standing waves in thin films is proposed in this paper and the diffraction intensity is calculated using the distorted-wave Born approximation (DWBA). Resonance enhancement in diffraction intensity is predicted. The intensity distributions of both the reflected diffracted beam and transmitted diffracted beam can now be calculated. The effect of the surface miscut is also included in the quantitative calculation. In general, the proposed new diffraction geometry can discriminate against substrate diffraction background, provide variable spatial concentration within the film sample, and be equally applied for X-rays as for neutrons.

Calculation of x-ray-diffraction profiles from vicinal surfaces.

We present a calculation of x-ray diffraction from a crystal with a surface oriented at an arbitrary angle relative to the axes of the bulk crystalline lattice, demonstrating that the scattering consists of rods in reciprocal space, each passing through a bulk peak and rotated away from the crystalline axes by an angle equal to the surface miscut. The cross-sectional profile of these rods is shown to be a direct probe of the surface height-height correlation function. For zero miscut, multiple rods overlap and previous results for flat surfaces are recovered. We consider the convolution of surface-diffraction profiles with a two-dimensional resolution function.

Pinned and unpinned step dynamics on vicinal silver (110) surfaces.

We present x-ray scattering and scanning-tunneling-microscopy studies of Ag(110) vicinally miscut along the [110] direction. For a clean surface miscut by 1 o we find no evidence for phase separation. However, for an impurity concentration of order ≤0.001 monolayer we find that the pinning of steps results in a phase separation into flat (110) terraces and densely stepped regions. With increasing temperature, the clean surface exhibits a rapid decrease in step-step correlations primarily along the [001] direction

The effect of external stress on Si surfaces

To study the effect of strain on surface properties, we had externally applied a continuously variable stress by loading cantilevered bars. The first experiments1 on nominally flat Si(100) produced asymmetries in the population of 2×1 and 1×2 domains which depended on the strain and not the gradient. The kinetics for the production and annealing of the asymmetry were identical and thermally activated, but the final steady state was temperature independent. The sense of the asymmetry is that the domain compressed along the dimer bond is favored. Alerhand et al.2 have suggested that the mechanism is the reduction of the energy in long range strain field due to the intrinsic surface stress. In this paper we compare the experimental observations and the expectation of the theory. We have now done the same experiments on a vicinal surface miscut by 1°. We have also observed the changes in the step (domain boundary) configurations in the STM. With an inadvertant miscut of 0.1°, the steps remain single height an...

Absorption effects from surface miscut in reflection diffractometry

The absorption effect due to a general surface miscut is given, and its reduction by averaging for an axis of rotation is shown.