X-ray Rocking Curve Measurements Research Articles

Growth of CdTe single crystals by vapour condensation on the surface of polycrystalline source material

A method of crystal growth from the vapour phase, which had been worked out for A IVB VI compounds, has been applied to CdTe. Single crystals shaped with (110) and (111) planes of approximately 10 mm size have been obtained. A high level of structure perfection has been confirmed by means of X-ray rocking curve measurements resulting in half-width values down to approximately 15″. The suitability for production of homogeneous CdTe-based A IVB VI solid solution crystals is discussed.

Low-temperature solid-phase heteroepitaxial growth of Ge-rich SixGe1−x alloys on Si (100) by thermal annealing a-Ge/Au bilayers

Heteroepitaxial layers of SixGe1−x alloys were grown on Si(100) by thermal annealing bilayers of a-Ge/Au deposited on single-crystal Si (sc-Si) substrates at 300 °C. During annealing, Ge dissolves into the Au layer and then grows epitaxially to the substrate, with the final structure changing from a-Ge/Au/sc-Si to Au/SixGe1−x/sc-Si. The SixGe1−x layer was found to be Ge rich (x≊0.15) from AES and STEM analysis and to be epitaxial to the Si(100) substrate from the x-ray rocking curve and RBS channeling measurements. Stacking faults and microtwins are the major defects in the epitaxial film, as observed by cross-sectional TEM. High-resolution TEM analysis of the SixGe1−x/Si interface shows that the growth initiates at specific areas of the original Au/Si interface. This work demonstrates for the first time both heteroepitaxial growth and the growth of SixGe1−x alloys on Si(100) using solid phase epitaxy with an eutectic-forming metal as the transport medium.

Characterization of ion-plated silicon nitride thin films

Abstract Silicon nitride (Si 3 N 4 ) thin films deposited at low (300 °C or below) substrate temperatures by an ion plating process are characterized. Amorphous, stoichiometric layers with hydrogen contents below 1 at.% are obtained. The microhardness is measured and the stress in the films is related to the process conditions. The adherence of the layers is illustrated by X-ray rocking curve measurements. Tests prove the excellent corrosion resistance Si 3 N 4 coatings for metallic substrates.

Accurate determination of misfit strain, layer thickness, and critical layer thickness in ultrathin buried strained InGaAs/GaAs layer by x-ray diffraction

We have analyzed data obtained from double-crystal x-ray rocking curve measurements to determine the lattice constants, strain relaxation, thickness, and critical thickness of a thin InxGa1−xAs layer embedded in GaAs. The use of a very wide x-ray scan angle (∼2.0°) allows the simultaneous determination of buried layer thickness and strain with greater accuracy. The critical thicknesses so obtained for buried InGaAs layers are smaller than that predicted by the energy balance model and larger than that predicted by the force balance model.

Raman Scattering Studies of Si1−xGex Layers Grown by Atmospheric Pressure Chemical Vapor Deposition

ABSTRACTRoom temperature Raman spectra are reported of Si1−xGex layers on Si substrates (for 0.08≤x≤0.2). The samples were grown using atmospheric pressure chemical vapor deposition techniques. Layer thicknesses varied from 0.1 — 10μm. The relative frequency shift of the Si-Si phonon mode for the SiGe strained epilayers from an incommensurate pseudo-alloy of the same composition is used as a quantitative measure of the lattice strain. For thicknesses below a critical value the Raman data indicate that the films are highly strained and the growth is commensurate with the substrate whereas thicker films are partially or fully relaxed. Phonon lines are sensitive to the interfaces and alloy layers. The results are consistent with other characterization studies, such as TEM and X-ray rocking curve measurements, of the same samples.

Chemical vapor deposition of β-SiC on silicon-on-sapphire and silicon-on-insulator substrates

Cubic silicon carbide (β-SiC) films have been grown epitaxially on silicon-on-sapphire (SOS) substrates by chemical vapor deposition. A fresh layer of silicon is first deposited in situ on the SOS substrate at approximately 1050°C. The silicon layer is then carbonized while being heated to 1360°C. The β-SiC layer is grown at 1360°C using silane and propane as sources. β-SiC films can also be grown directly on the SOS substrate without utilizing a fresh silicon layer. Deposition of β-SiC films on silicon-on-insulator (SOI) substrates has also been accomplished with slight modification of the growth parameters described above.The β-SiC films have been characterized by IR reflectance spectroscopy, optical microscopy and electron microscopy. Typical films are 7 μm thick and have a specular surface with some physical features. Electrical transport properties as determined by the Van der Pauw Hall method show the β-SiC films to be p-type while those grown on SOI were n-type. X-ray rocking curve measurements were obtained to determine the crystalline quality of the films. In addition, preliminary optical characterization of the films has been performed.

Single and double buried epitaxial metallic layers in Si prepared by ion implantation

In recent years, heteroepitaxial structures of CoSi 2/Si and Si/CoSi 2/Si have become an important topic of fundamental studies, as well as of novel device applications. The usual method for preparation of such structures is deposition of Co or CoSi 2 with techniques such as molecular beam epitaxy (MBE). Ion beam synthesis (IBS) is another attractive method which has been developed recently. With this new technique, heteroepitaxial surface and buried CoSi 2 layers with thicknesses from 160 to 1100 Å have been formed successfully. RBS, channeling, cross-sectional TEM, Mössbauer spectroscopy and X-ray rocking curve measurements have been used to study the thickness, the crystalline quality, the abruptness of the interfaces, the chemical phase, the strain and the orientation of both the surface and buried CoSi 2 layers. The results show that the quality of surface and buried CoSi 2 layers formed by IBS is as good as those formed by MBE. The measured values for the strain are found to be far below the value expected for pseudomorphic layers, and show no clear correlation with the layer thickness. On the other hand, we observed a remarkable correlation between the thickness of the buried layer and its orientation: the orientation ranges from 100% type A orientation (parallel with the Si substrate) for a thick layer (thicker than 360 Å) to as much as 70% type B (antiparallel with the Si substrate) for thinner layers. This phenomenon is interpreted as an equilibrium between two driving forces. Recently, we made the first double heterostructures by ion implantation at two different energies. After annealing, a Si/CoSi 2/Si/CoSi 2/Si-substrate structure with two buried CoSi 2 layers was obtained. The thinnest (160 Å) has a pure type B orientation while the thickest layer (600 Å) has pure type A orientation. This result fully fits in the thickness dependence of the orientation we found for single CoSi 2 layers.

Rapid Structural Defect Mapping of Bulk II-VI Semiconductors Using White-Beam Synchrotron Topography and X-ray Rocking Curve Analysis

ABSTRACTNondestructive characterization techniques for substrates, epilayers, and device structures are becoming increasingly important in the semiconductor industry. Synchrotron-based white-beam x-ray topography, x-ray rocking curve measurements, and etch pit density were used to map the defect structure in a variety of CdTe and CdZnTe single crystal substrates, which are important for IR detector applications involving HgCdTe. Defects such as low angle grain boundaries have been successfully correlated using topography, rocking curves, and etch pit density, and twins have been observed using topography and rocking curves. The effectiveness of white-beam synchrotron topography for rapid and nondestructive defect analysis and substrate screening is discussed.

Deposition and Characterization of MgO Thin Films on SrTiO3 and LaAlO3 Substrates

ABSTRACTMgO thin films have been deposited on SrTiO3 and LaA1O3 substrates using both off-axis rf magnetron sputtering and electron beam evaporation techniques. The effects of substrate material, temperature, film thickness, deposition rate, sputtering gas, and pressure on the quality of the MgO films produced have been studied. Films deposited on (100) SrTiO3 at temperatures > 300°C display only the (h00) reflections in their X-ray diffraction traces, with narrow X-ray rocking curve measurements indicating that these films are epitaxial. Epitaxy has been confirmed with grazing incidence diffraction. MgO films deposited on (100) LaAlO3 are crystalline, but have varying orientations depending on the film thickness. From scanning electron microscopy, MgO films on SrTiO3 substrates appear smooth and dense while those deposited on LaAlO3 substrates possess rougher surfaces. Surface morphologies have been analyzed using atomic force microscopy.

Detection of the EL2 metastability by x-ray rocking-curve measurements at low temperatures

X-ray experiments are usually seen as a tool for studying large lattice imperfections. We present for the first time experimental evidence obtained from x-ray measurements that metastable behavior of the EL2 defect in semi-insulating GaAs can be connected with crystal lattice relaxation. New unexpected results showing change of the lattice state while cooling semi-insulating GaAs samples in darkness are also reported.

High-energy Si implantation into InP:Fe

High-energy Si implantations were performed into InP:Fe at energies ranging from 0.5 to 10 MeV for a dose of 3×1014 cm−2, and at 3 MeV for the dose ranging from 1×1014 to 2×1015 cm−2. The first four statistical moments of the Si-depth distribution, namely range, longitudinal straggle, skewness, and kurtosis, were calculated from the secondary-ion mass spectrometry (SIMS) data of the as-implanted samples. These values were compared with the corresponding trim-89 calculated values. SIMS depth profiles were closely fitted by Pearson IV distributions. Multiple implantations in the energy range from 50 keV to 10 MeV were performed to obtain thick n-type layers. Variable temperature/time halogen lamp rapid thermal annealing (RTA) cycles and 735 °C/10-min furnace annealing were used to activate the Si implants. No redistribution of Si was observed for the annealing cycles used in this study. Activations close to 100% were obtained for 3×1014-cm−2 Si implants in the energy range from 2 to 10 MeV for 875 °C/10-s RTA. Transport equation calculations were used to interpret low activation results for high dose Si implants. Polaron electrochemical C–V profiling was used to obtain carrier concentration depth profiles. The lattice quality of the as-implanted and annealed material was evaluated by performing x-ray rocking curve measurements.

In situ determination of phosphorus composition in GaAs1−xPx grown by gas-source molecular beam epitaxy

We report for the first time an in situ determination of phosphorus compositions in a mixed group-V compound, such as GaAs1−xPx, grown by gas-source molecular beam epitaxy. Reflection high-energy electron diffraction intensity oscillations from As-limited and (As+P)-limited growth are observed on a Ga-rich GaAs surface. The phosphorus composition is therefore deduced from the different growth rates. Viability of this technique is strongly confirmed by the good agreement with the phosphorus compositions determined ex situ by x-ray rocking curve measurements on GaAs/GaAsP strained-layer superlattice structures.

Determination of different orientations in epitaxial silicide layers using X-ray diffraction

Heteroepitaxial CoSi2 layers have been formed by high-dose ion beam synthesis and solid phase epitaxy on Si(111) substrates. X-ray rocking curve measurements allow a very precise determination of the relative amounts of aligned (type A) and twinned (type B) CoSi2. A simple procedure yields the separation of the asymmetric reflections of the (331) planes of type A or type B Si and CoSi2. the intensity ratio of the (331) reflection of type A and type B CoSi2 corresponds to the relative amounts of type A and type B CoSi2.

Assessment of mismatched epitaxial layers by X-ray rocking curve measurements and simulations

In the design of heteroepitaxial systems the knowledge of composition, strain and thickness of the various layers involved is of great importance. The determination of these structural parameters is among the applications most common in high-resolution X-ray diffraction. Numerical simulation of rocking curves has emerged as an important aid in the determination of the relevant structural parameters. Based upon the dynamical theory of X-ray diffraction a FORTRAN program has been written to simulate and refine structural parameters from rocking curve data. X-ray rocking curve analysis has been used to develop and optimize MOCVD-growth of Ga x In 1- x P/GaAs heteroepitaxial systems. We observed superlattice peaks in samples of low misfit. With the aid of computer simulations we attribute these to unintentional periodic compositional fluctuations (Ga/In) of the order of 1%.

Be, S, Si, and Ne ion implantation in InSb grown on GaAs

Single- and multiple-energy Be, S, Si, and Ne ion implantations were performed at room temperature in InSb grown on semi-insulating GaAs substrates. The implanted material was subjected to both isochronal and isothermal annealing schemes. The as-implanted and annealed material was characterized by Hall, secondary ion mass spectrometry, and x-ray rocking curve measurements. The as-implanted material is highly n-type for all implant species used in this study. A maximum p-type activation of 90% and n-type activation of 16% was achieved for Be and S implants, respectively. Be activation depends on the thickness of the InSb layer. No in-diffusion of Be and S was observed even after 500 °C anneal. The Si implant has an amphoteric doping behavior.

Strain and orientation in epitaxial CoSi 2(111) layers formed by ion implantation

Strain and orientation in epitaxial CoSi 2(111) layers formed by ion implantation have been studied by RBS/channeling and X-ray rocking curve measurements. For the thickness range (20–47 nm) of the epilayers studied, the average misalignment ΔΨ ( Ψ = 35.26°) and perpendicular strain ϵ ⊥ xare 0.30° and −1.87% respectively, which shows that the strain in our epilayers is larger than in the thicker layers prepared by ion implantation and in the MBE grown layers with similar thickness range, but it is still far from a completely strained layer. Our results also confirm that a pure type A or predominant type A oriented epitaxial CoSi 2 layer, which is rather difficult to prepare by the conventional UHV procedure, can easily be formed by ion implantation. However, for epilayer thicknesses lower than 36 nm, a correlation between the epilayer thickness and orientation is clearly present.

X-ray rocking curve measurement of composition and strain in Si-Ge buffer layers grown on Si substrates

The level of strain and the fraction of Ge in SiGe layers grown on Si can be found rapidly and unambiguously using double-crystal x-ray diffraction and a simple application of the linear elasticity theory combined with Vegard’s law. The method gives excellent results for 0.4-μm-thick buffer layers of SiGe/Si containing 5%–50% germanium. It is shown that lattice relaxation rises abruptly at x(Ge)≥15%, and that some strain remains for x(Ge) as high as 50%.

Optically pumped [formula omitted] lasers on [formula omitted] substrates

Optically pumped lasing has been observed up to 100 K in a Cd 0.2Zn 0.8Te ZnTe superlattice grown on a GaAs Si substrate. At 100 K, rapid degradation of the lasing signal is seen. This result is inferior to that previously reported for a similar structure grown on a GaAs bulk substrate, for which room-temperature lasing was seen with no degradation. X-ray rocking curve and morphology measurements suggest that the II–VI epilayer has limited ability to heal the extra defects that are present when a GaAs Si , rather than a bulk GaAs, substrate is used.

Elucidation of Deformation and Recovery Mechanism in Nickel-Base Alloy 600 by X-Ray Rocking Curve Measurements

Elucidation of Deformation and Recovery Mechanism in Nickel-Base Alloy 600 by X-Ray Rocking Curve Measurements

Defect Model and Growth Characteristics of Low Temperature GaAs

ABSTRACTLow-temperature GaAs layers (LTGaAs) grown by molecular beam epitaxy on GaAs substrates have been characterized by x-ray diffraction techniques. X-ray rocking curve measurements on more than 200 anneal conditions show that through appropriate choice of growth condition, layers with different states of strain are obtained. Three distinct ranges of low temperature growth are defined, labelled as “low-range,” “mid-range,” and “high-range,” corresponding to growth temperatures less than 260 °C, between 260 and 450 °C, and more than 450 °C, respectively. 0.5μm thick films grown in the low-range are amorphous, whereas those in the mid-range are fully strained and lattice-matched to the substrate, and those grown above 450 °C are indistinguishable from ordinary GaAs. Notable properties of mid-range layers are the random behavior of the as-grown strain, and the expansion and contraction of the lattice parameter with thermal anneals up to 900 °C. A growth model for LTGaAs based on arsenic antisite defects is proposed.