X-ray Reflectivity Spectroscopy Research Articles

Atomic Hydrogen Assisted Growth of Si-Ge Heterostructures on (001) Si

AbstractA study of the interface chemical and physical abruptness of Si-Ge heterostructures grown on (001) Si by molecular beam epitaxy under atomic hydrogen exposure is reported. Atomic hydrogen (AH) was produced by the dissociation of molecular hydrogen interacting with a hot tungsten filament. Secondary-ion mass spectroscopy (SIMS) of structures made of alternating Ge (0.5 nm)/Si (40 nm) layers demonstrated that AH can effectively suppress Ge surface segregation. The segregation length was reduced from 1.5 nm to about 0.5 nm in films grown at a hydrogen partial pressure of −5 × 10-3 Pa and cell temperature of 2140 °C with an estimated cracking efficiency of ~5%. However, the high hydrogen background pressure had detrimental effects on the physical sharpness of the interfaces. This was evidenced by comparing the interface quality of Si/Ge atomic layer superlattices grown with and without AH exposure. X-ray reflectivity and Raman spectroscopy revealed a significant increase of the interface roughness, although the periodic character and the good crystallinity of the structures were preserved.

Pulsed-Laser Deposition and Characterization of Amorphous Diamondlike Carbon Films

ABSTRACTUnhydrogenated amorphous carbon films were deposited by KrF pulsed laser ablation of graphite under a laser power density of 8×108 W/cm2. The films were characterized using x-ray reflectivity, optical transmittance, spectroscopic ellipsometry and Raman spectroscopy. The physical, optical and bonding properties of the films have been investigated in detail as functions of substrate temperatures Ts (22-300°C) and post-annealing temperatures. Films deposited at Ts, <200°C possessed diamond-like properties with mass densities p=2.8-3.1 g/cm3 and optical bandgaps Eg,=1.5-2.2 eV. Above Ts,=200°C, the films showed typical graphite characteristics. The diamond-like films annealed at temperatures up to 750°C show excellent thermal stability.

Structure of Co/Cu multilayers studied by x-ray diffraction and x-ray absorption spectroscopy.

Co/Cu (111) textured multilayers prepared in ultrahigh vacuum by thermal evaporation on a gold substrate have been characterized by x-ray diffraction, x-ray reflectivity, and x-ray absorption spectroscopy. The extended x-ray absorption fine-structure measurements show that in the plane of the layers, the Co lattice is slightly expanded and the Cu lattice is slightly contracted to compensate for the mismatch. The lattice strain is negligible in the growth direction. Copper layers have a highly ordered fcc structure. Cobalt layers, mainly fcc with several stacking faults, are locally much more disordered than copper layers.

Correlation between X-Ray Reflectivity and Rutherford Backscattering Spectroscopy for Density Measurement of Thin Films

The film density of nickel was examined by means of X-ray reflectivity measurement and Rutherford backscattering spectroscopy (RBS). The Ni thin film was deposited by electron beam evaporation in a high-vacuum system and was annealed to change its density. The density of the as-deposited film was 7.8±0.1 g/cm3. A good correlation between the X-ray reflectivity measurement and RBS was demonstrated.

The growth of indium on the Si(111) surface studied by X-ray reflectivity and Auger electron spectroscopy

The growth of indium on the 7 × 7 reconstructed (111) surface of silicon has been studied as a function of substrate temperature by X-ray reflectivity and Auger electron spectroscopy. A correlation is seen between features in the X-ray reflectivity curves and breaks in the Auger signal versus time plot. The oscillation of the X-ray signal indicates that below 400°C two consecutive pseudomorphic indium layers are formed before three-dimensional islanding occurs. Kinematic analysis predicts the shape of the X-ray signal versus time curve and yields the perpendicular displacement of the indium layers from the substrate. It is proposed that the first layer of indium atoms are bonded vertically above the top most layer of silicon atoms in T 1 sites.

The growth of indium on the Si(111) surface studied by X-ray reflectivity and Auger electron spectroscopy

The growth of indium on the Si(111) surface studied by X-ray reflectivity and Auger electron spectroscopy

Characterization of thin films of amorphous GaP using optical and electron spectroscopy

Thin films of flash-evaporated GaP were examined by reflectance-transmittance techniques, spectroscopic ellipsometry in the visible range, grazing-incidence X-ray reflectivity and Auger electron spectroscopy. The interfaces of the film with both the substrate and the atmosphere are oxidized. A multilayer structure is proposed from the ellipsometry data and compared with the results of the X-ray and Auger analyses.