X-ray Diffraction ) And Cross-sectional Transmission Electron Microscopy Research Articles

Structural characterization of cubic and hexagonal GaN thin films grown by IBA–MBE on SiC/Si

Buried ion beam synthesized 3C-SiC layers were revealed to the surface of silicon wafers to provide lattice matched substrates for GaN thin film epitaxy. Both epitaxial SiC/Si(1 1 1) and SiC/Si(0 0 1) growth surfaces with either six- or four-fold crystal symmetry, respectively, were formed. GaN thin film growth was achieved by ion beam assisted molecular beam epitaxy (IBA–MBE) which – owing to the energy and momentum transfer of the ions – allows to deposit epitaxial thin films at particularly low growth temperatures where both the stable hexagonal and the metastable cubic polytype of GaN can be formed. It is shown by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) that using appropriate fluxes of Ga atoms both purely hexagonal and purely cubic GaN films can be grown epitaxially on SiC/Si(1 1 1) and SiC/Si(0 0 1), respectively. Thereby Ga rich growth conditions seem to stabilize the formation of the cubic polytype. It is obvious from XTEM studies that the high density of crystal defects in the SiC layer is not transferred onto the growing GaN films and that the crystalline quality of GaN films improves with increasing film thickness. The influence of surface roughness and wettability, interfacial cavities and the nucleation of twin-type defects at the GaN/SiC interface on the crystalline quality of the GaN thin films is discussed.

Blistering/exfoliation kinetics of GaAs by hydrogen and helium implantations

The blistering and exfoliation kinetics of GaAs (100) wafer implanted by hydrogen and helium were studied. The influence of ion fluence, implantation and subsequent annealing temperatures on the blistering and/or exfoliation was studied by Rutherford Backscattering Spectroscopy (RBS), optical microscopy, high resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The optimum H + fluence for the GaAs blistering after annealing in the 160–350 °C temperature range was of 1–2 × 10 17 H +/cm 2 for implantation temperatures of 120–160 °C. An avalanche type exfoliation was found in the GaAs wafer implanted at room temperature with 100 keV helium ions at fluences of 2–5 × 10 16 He +/cm 2 after annealing in the 200–300 °C. In case of helium implantation, a notable dependency of the exfoliated depth on the fluence was found: XTEM analysis showing dislocation-bubble lines that serve as a fracture path for exfoliation.

Characterization of orientation-selective-epitaxial CeO2 layers on Si(100) substrates by x-ray diffraction and cross-sectional transmission electron microscopy

Orientation-selective-epitaxially grown CeO2 layers on Si(100) substrates are characterized by x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). XRD analyses prove how diffraction intensities of CeO2 (200) and (220) peaks vary depending on substrate bias under which the layers grew. It is confirmed that (200) and (220) peaks reach maxima at ±15 and 0V biases, respectively, where they are pure single crystalline of respective orientations. Samples grown at other bias have both (200) and (220) peaks, whose peak intensity ratio varies as the bias voltage departs from above three values. These results agree well with the reported results by reflection high energy electron diffraction analyses. XTEM observations are carried out utilizing focused ion beam technology in sample fabrication. In CeO2(110)∕Si(100) samples, interfacial amorphous layers are seen, which are similar with commonly reported results. XTEM lattice images clarify the nonexistence of interfacial amorphous la...

Structural Analysis of Nanocrystalline Silicon Prepared by Hot-wire Chemical Vapor Deposition on Polymer Substrates

AbstractNanocrystalline silicon (nc-Si:H) films were deposited by hot-wire chemical vapor deposition (HWCVD) directly onto Corning glass and polyimide (Kapton E) substrates. The effect of silane concentration (in hydrogen carrier gas) on film crystallinity and conductivity were studied for a constant substrate growth temperature of 220°C. Raman spectroscopy, X-ray diffraction and cross-sectional transmission electron microscopy (XTEM) showed that nc-Si:H (grain-size 20-65 nm) was observed for silane concentrations below 5.8 %. Similar to previous reports, closer inspection using XTEM found that there was an initial growth of an amorphous interfacial layer which then crystallized into a randomly-oriented polycrystalline material after 10 - 100 nm of growth.. However, unlike previous reports, there was no detectable difference in the structure or conductivity for films grown on the two types of substrates. In both cases, the dark conductivity decreased with increasing silane concentration while the photo-conductivity was uniform for all films at values between 2 and 4×10-5 S/cm.

Microstructural evolution of Fe/Ti multilayers submitted to in situ thermal annealing

The Fe/Ti multilayers of nominal bilayer thickness of 4.0, 8.0 and 18.0 nm with alternating Fe and Ti sublayers thickness ratio of 1:1 were deposited by direct current magnetron sputtering on Si(100) substrates. The bilayer thickness of as-deposited Fe/Ti multilayers was measured as a modulation wavelength of 4.8, 8.5 and 19.0 nm, respectively, by small angle X-ray diffraction and cross-sectional transmission electron microscopy (XTEM). The three Fe/Ti multilayers were composed of pure metallic α-Fe and α-Ti according to wide angle X-ray diffraction and selected area diffraction. The Fe/Ti multilayers were in situ submitted to thermal vacuum annealing at the temperatures ranging from 523 K to 723 K for the annealing time of 3 h. With annealing at the lower temperature of 523 K, the intermetallic FeTi appeared in the Fe/Ti multilayers with small modulation wavelength of 4.8 nm. At 623 K, the intermetallic FeTi was formed with modulation wavelength of 8.5 nm. At the higher temperature of 723 K, the intermetallic FeTi was detected with modulation wavelength of 19.0 nm. The modulation wavelength of the Fe/Ti multilayers remained during the thermal annealing. The mixture of intermetallic FeTi and α-Fe phase was observed in the extended Fe sublayer of the Fe/Ti multilayers annealed at 723 K by XTEM, correspondingly the remaining Ti sublayer was obtained as a thinned sublayer. Coexistence of the intermetallic FeTi, α-Fe and α-Ti phases indicated that the dynamic factors have control of the intermixing between the Fe and Ti sublayers in the Fe/Ti multilayers during the thermal annealing.

Growth of II-IV-V2 chalcopyrite nitrides by molecular beam epitaxy

Synthesis of crystalline MgGeN2 thin solid films is achieved using the technique of molecular beam epitaxy (MBE). The details of the epitaxial process are described. The microstructures of these films are investigated by both x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Comparison of the lattice structure with powder diffraction standards suggests the lattice structure may be orthorhombic with a high degree of texture. Morphology is evaluated by atomic force microscopy, and a periodic pattern of growth mounds is observed. A formalism for dynamical roughening is applied to quantify the mounded surface features. Mounds are found to have an average spacing of 235 nm, and the surface exhibits a saturation value of 22 nm for the root mean correlated height difference. Diffusion bias is discussed as a mechanism for the formation of surface mounds.

FORMATION OF NOVEL Cu3Au ALLOY PHASE UNDER CONFINEMENT

Our present work deals with the formation and thermal behavior of a nonbulk alloy phase confined within about 8 nm across the interfaces of Au/Cu multilayer systems. These multilayers deposited on silicon and float glass by DC magnetron sputtering have been studied by secondary ion mass spectrometry (SIMS), X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Along with the highly oriented growth of the Cu and Au layers along [111], Cu 3 Au alloy was found to be present only at the Cu/Au interfaces in the nonbulk tetragonal D023 phase. Co -sputtering of Au and Cu under similar conditions produces only conventional fcc Cu 3 Au alloy phases, suggesting that interfacial confinement plays a significant role in producing the novel Cu 3 Au alloy phase in gold/copper multilayers. This novel phase is found to form only when the interfacial width is less than 10 nm. The D023 alloy phase tends to stabilize, rather than transforming to the bulk L12 phase, when the multilayer is vacuum-annealed at 150°C. As alloy formation spreads out of the interfaces (on vacuum annealing at 200°C), the dominant alloy is CuAu , consistent with the Cu:Au atomic ratio averaged over the multilayer.

Diffusion limited Cu and Au nanocrystal formation in thin film SiO2

Elemental Cu and Au nanocrystals (NCs) were produced by high-energy ion-implantations into amorphous silica (SiO2) and subsequent thermal annealing. By a combination of X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) we confirm both NC species to have the bulk face-centered cubic phase and estimate their average diameter. We concentrate on the investigation of the concentration and size-dependent coordination number (CN) of these matrix embedded NCs utilising extended X-ray absorption fine structure (EXAFS) spectroscopy. The CN is found to be suppressed compared to that of a bulk standard. The CN in Au NCs is found to be lower than that of Cu NCs in agreement with smaller average Au NC sizes. We explain this difference by the difference in diffusivity for the two atomic species in SiO2.

Characterization of Nanoclusters in MgO Created by Means of Ion Implantation.

ABSTRACTMetal nanoclusters (NCs) of lithium, zinc, silver and gold embedded in MgO were created by means of ion implantation of Li, Zn, Ag and Au ions into single crystals of MgO(100) and subsequent thermal annealing. Nanoclusters of the compound semiconductor CdSe were obtained by implantation of both Cd and Se ions. Solid noble gas clusters were formed by Kr ion implantation. Optical and structural properties of the NCs were investigated using optical absorption spectroscopy (OAS), high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The mean nanocluster size is estimated from the broadening of the Mie plasmon optical absorption bands using the Doyle formula. These results are compared with the NC size as obtained from XRD (using the Scherrer formula) and from direct XTEM observations. The three methods are found to be in reasonable agreement with a mean size of 4.0 and 10 nm found for the Au and Ag clusters, respectively. Using TEM observations, the relative interface energies of MgO//Au and MgO//Ag interfaces are also determined. In the case of MgO//Au, they are found not to be in agreement with theoretical predictions in the literature. CdSe nanoclusters were found to adopt different crystal structures dependent on the size. Small ones (<5 nm) appear to have a rock salt structure, larger ones the sphalerite structure. The solid krypton NC's are under high pressure. The pressure of individual Krypton bubbles was determined from the moiré fringes

Structural properties of Au and Ag nanoclusters embedded in MgO

Gold and silver nanoclusters embedded in MgO were created by means of ion implantation of 1.0 MeV Au or 600 keV Ag ions to a dose of 10 16 cm −2 into single crystals of MgO(1 0 0) and subsequent annealing at 1473 K for a period of 22 h. The structural properties of the nanoclusters were characterised by optical absorption spectroscopy (OAS), high-resolution X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Nanocluster sizes are estimated using three different methods: using the Doyle formula for the broadening of the optical absorption peak associated with Mie plasmon resonance; using the Scherrer formula for the broadening of the Au and Ag XRD peaks, and from direct observation of TEM images. For the Au clusters, the methods are in excellent agreement with mean cluster sizes of 4–5 nm. For the Ag clusters, the optical Doyle method yields a mean nanocluster size of 5 nm while the XRD and XTEM methods yield 10–11 nm. The XRD and XTEM results reveal a cube-on-cube orientation relationship of the Au and Ag nanoclusters with respect to the MgO matrix.

Industrial application of WC–Ti (1− x) Al xN nanocomposite films synthesized by cathodic arc ion plating process on a printed circuit board drill

New WC–Ti (1− x) Al x N nanocomposite films were synthesized on Si wafer WC–Co substrate by cathodic arc ion plating. A rotating substrate holder operated at 6 rev./min was used to obtain a layered structure, and the arc power density of Al cathodes was controlled for the change of Al concentration ( x) in the film. For the evaluation of crystal structure and compounds formation behavior, X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) analyses were performed. The microhardness of WC–Ti (1− x) Al x N films was measured at a normal load of 30 mN by a nano-indentation instrument. WC–Ti 0.43Al 0.57N nanocomposite film that revealed the highest hardness and good adhesion strength were applied to a printed circuit board (PCB) drill for the evaluation of the drill's lifetime. As a result of adapting a PCB drill coated with WC–Ti 0.43Al 0.57N film, the lifetime of the PCB drill was improved by more than two times than that of the ordinary one.

Plasma vapor deposition hard coating on pre-nitrided low alloy steel

Ion-nitrided samples of the hardened and tempered low alloy steel 40Cr was coated by a TiN layer by hot chemical deposition (HCD) ion plating. By this complex treatment combining ion-nitriding with subsequent ion plating, the surface hardened layer was composed of a thin outermost coating layer of TiN with a hardness of approximately 2300 Hv, a thin compound layer of ε+γ′ with a hardness of 800–1000 Hv and a thicker inner diffusion layer of approximately 600–800 Hv. X-Ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) results showed that a α-Fe layer (black layer) is not observed on the interface between compound layer and TiN layer after duplex treatment. At the interface, Ti reacted with N from the compound layer to form a TiN layer and ε-Fe 2–3N transformed into γ′-Fe 4N partially.

Supersonic jet epitaxy of silicon carbide on silicon using methylsilane

Cubic SiC thin films have been epitaxially grown on silicon substrates using the single source precursor methylsilane (H 3Si–CH 3). Single phase films were grown by supersonic jet epitaxy (SJE) at temperatures as low as 560°C on Si(111) and 600°C on Si(001). Growth rates and crystal quality were found to be strongly dependent on substrate temperature and methylsilane kinetic energy. Films were characterized by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM).

Microstructure in sputtered Co/sub 90/Fe/sub 10//Ag GMR multilayers

The microstructure of Co/sub 90/Fe/sub 10//Ag GMR multilayer films has been investigated using X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Columnar grain growth with a (111) fiber texture is observed. A direct correlation is made between superlattice satellite peak signals from selected area electron diffraction (SAD) and XRD.

Investigation of film growth for amorphous Nb/Si multilayers

In this letter, film growth for amorphous Nb/Si multilayers has been studied by using x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). Results from XRD and XTEM show that the structures of amorphous Nb/Si multilayers deposited at room temperature and 550 °C are quite different. The influences of surface mobility of adatoms and interfacial reaction on interfacial roughness are discussed.

Characterization of Tib2/TISI2 Bilayer Structure Deposited by Sputtering

AbstractBilayer of TiB2/TiSi2 was deposited by magnetron co-sputtering on silicon and alumina substrates, and this structure was investigated for structural and electrical properties. Substrate bias and annealing in vacuum have been applied to vary the film properties. X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) were used to characterize the structure, and chemical composition was characterized by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). Resistivity was measured by four probe method. Diffusion barrier properties were studied by AES. As deposited films are amorphous with resistivities of about 40 μΩcm. Post deposition annealing in vacuum shows that the amorphous titanium boride film is very stable. Crystallization starts above 1000°C as seen by XRD, and the crystallization temperature depends on the thickness of TiB2. TiSi2 C54 forms in the temperature range 586°C - 922°C, when TiB2 still remains in amorphous form. The TiSi2 sublayer serves as an additional effective diffusion barrier, preventing outdiffusion of boron from TiB2 into the Si substrate.

In situ magnetic and structural analysis of epitaxial Ni80Fe20 thin films for spin-valve heterostructures

We have investigated structural and magnetic properties of epitaxial (100) Ni80Fe20 films grown on relaxed Cu/Si(100) seed layers. The crystallographic texture and orientation of these films was analyzed in situ by reflection high energy electron diffraction (RHEED), and ex situ by x-ray diffraction and cross-sectional transmission electron microscopy (XTEM). In particular, RHEED intensities were recorded during epitaxial growth, and intensity profiles across Bragg rods were used to calculate the surface lattice constant, and hence the film strain. XTEM analysis indicated that the epitaxial films had atomically abrupt interfaces. The magnetic properties of these epitaxial films were measured in situ using magneto-optic Kerr effect magnetometry. Large Hc (10–20 Oe) was observed for epitaxial Ni80Fe20 (100) films less than 10.0 nm thick whereas for larger thicknesses, Hc decreased to a few Oe with the appearance of a uniaxial anisotropy. Correlations were made between magnetic properties of these epitaxial films and the strain in the film.

Study of the structure of sputter-deposited Ni-Si multilayers

In this paper low angle X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) studies of as-sputtered Ni-Si multilayers are reported. The modulation period, average composition and interfacial roughness determined from low-angle XRD combined with optical theory are compared with XTEM results. The relative importance of the effect of interface roughness on the modulated structure and the relation between the modulation period and the solid state amorphization reaction in the as-sputtered Ni-Si multilayers are discussed.

In Situ Analysis of magnetic and Structural Properties of Epitaxial and Polycrystalline Ni80Fe20 Thin Films

ABSTRACTWe have investigated structural and magnetic properties of epitaxial Ni80Fe20 films grown on relaxed epitaxial Cu/Si (001) films. The crystallographic texture of these films was analyzed in situ by reflection high energy electron diffraction (RHEED), and ex situ by x-ray diffraction and cross-sectional transmission electron Microscopy (XTEM). In particular, RHEED intensities were recorded during epitaxial growth, and intensity profiles across Bragg rods were used to calculate the surface lattice constant, and hence, find the critical epitaxial thickness for which Ni80Fe20 grows pseudomorphically on Cu (100). XTEM analysis indicated that the epitaxial films had atomically-abrupt interfaces which was not the case for polycrystalline Cu and Ni80Fe20 film interfaces. The Magnetic properties of these epitaxial films were Measured in situ using Magneto-optic Kerr effect magnetometry and were compared with those of polycrystalline films grown on SiO2/Si. Large Hc (∼ 35 Oe) was observed for epitaxial Ni80Fe20 films less than 3.0 nm thick whereas for increasing thickness, Hc decreased approximately monotonically to a few Oersteds. Correlations were made between magnetic properties of these epitaxial films, the strain in the film and the interface roughness obtained from XTEM analysis.

Structural Characterization of P-I-N Diode Superlattice Structures Grown on <100>, <110>, and <111> Orientation Si Substrates

ABSTRACTP-I-N diodes whose intrinsic region consists of strained layer superlattices (SLS), separated by 40 nm Si spacers, have been grown by MBE on Si substrates with <100>, <110>, and <111> orientations. These structures have been characterized by x-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM). The dual periodicities in these structures produced unique XRD effects and the quality was highly dependent on substrate orientation. The <100> sample was in general free of defects, whereas the <110> and <111> specimens contained significant numbers of twins and dislocations.