Structural and Optical Properties of Amorphous Ge2Sb2Te5

2006 ◽  
Vol 918 ◽  
Author(s):  
Heng Li ◽  
T. Ju ◽  
T. Herring ◽  
P. C. Taylor ◽  
D. L. Williamson ◽  
...  
Keyword(s):  
Growth Rates ◽  
Local Strain ◽  
Band Tail ◽  
Tail Region ◽  
Local Strains ◽  
Force Microscopy ◽  
Oxygen Incorporation ◽  
Preparation Conditions ◽  
Atomic Force ◽  
20 Nm

AbstractThe optical and structural properties of amorphous sputtered films of Ge2Sb2Te5 depend strongly on the preparation conditions. Films grown at higher growth rates exhibit greater local strains as indicated by the slope of the optical absorption in the exponential “band-tail” region, but these films also incorporate smaller densities of oxygen impurities. At slower growth rates the band-tail slopes are sharper (smaller local strains) but there is greater oxygen incorporation. We will discuss several experiments that suggest that the local strain relief in the films grown at slower growth rates is due to a greater ability of the atoms to rearrange on the growing surface and not to increased oxygen incorporation. Small angle x-ray scattering experiments show that the films exhibit small elliptical “voids” with long axes perpendicular to the growing surface. The approximate dimensions of these voids are 3 × 20 nm. These films can be switched optically with little change in surface topography as measured by atomic force microscopy. Electron spin resonance measurements indicate that paramagnetic defects exist in some films but are either absent or below the detection limit (~ 1018 cm-3) in most films. The implications of these results for the switching mechanisms will be discussed.

ATOMIC FORCE MICROSCOPY AND XRD ANALYSIS OF SILVER FILMS DEPOSITED BY THERMAL EVAPORATION

2006 ◽  
Vol 20 (02) ◽  
pp. 217-231 ◽  
Author(s):  
MUHAMMAD MAQBOOL ◽  
TAHIRZEB KHAN
Keyword(s):  
Atomic Force Microscopy ◽  
Grain Size ◽  
Surface Characterization ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Xrd Analysis ◽  
Force Microscopy ◽  
Atomic Force ◽  
Average Grain Size ◽  
20 Nm

Thin films of pure silver were deposited on glass substrate by thermal evaporation process at room temperature. Surface characterization of the films was performed using X-ray diffraction (XRD) and atomic force microscopy (AFM). Thickness of the films varied between 20 nm and 72.8 nm. XRD analysis provided a sharp peak at 38.75° from silver. These results indicated that the films deposited on glass substrates at room temperature are crystalline. Three-dimension and top view pictures of the films were obtained by AFM to study the grain size and its dependency on various factors. Average grain size increased with the thickness of the deposited films. A minimum grain size of 8 nm was obtained for 20 nm thick films, reaching 41.9 nm when the film size reaches 60 nm. Grain size was calculated from the information provided by the XRD spectrum and averaging method. We could not find any sequential variation in the grain size with the growth rate.

Growth and Characterization of bulk GaN by Ga Vapor Transport

2004 ◽  
Vol 831 ◽  
Author(s):  
Phanikumar Konkapaka ◽  
Huaqiang Wu ◽  
Yuri Makarov ◽  
Michael G. Spencer
Keyword(s):  
Growth Rates ◽  
Vapor Transport ◽  
Spiral Growth ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Bulk Gan ◽  
Diffraction Patterns

ABSTRACTBulk GaN crystals of dimensions 8.5 mm × 8.5 mm were grown at growth rates greater than 200μm/hr using Gallium Vapor Transport technique. GaN powder and Ammonia were used as the precursors for growing bulk GaN. Nitrogen is used as the carrier gas to transport the Ga vapor that was obtained from the decomposition of GaN powder. During the process, the source GaN powder was kept at 1155°C and the seed at 1180°C. Using this process, it was possible to achieve growth rates of above 200 microns/hr. The GaN layers thus obtained were characterized using X-Ray diffraction [XRD], scanning electron microscopy [SEM], and atomic force microscopy [AFM]. X-ray diffraction patterns showed that the grown GaN layers are single crystals oriented along c direction. AFM studies indicated that the dominant growth mode was dislocation mediated spiral growth. Electrical and Optical characterization were also performed on these samples. Hall mobility measurements indicated a mobility of 550 cm2/V.s and a carrier concentration of 6.67 × 1018/cm3

Spectroscopic Characterization of Flame-Generated 2-D Carbon Nano-Disks

2015 ◽  
Vol 1726 ◽  
Author(s):  
Patrizia Minutolo ◽  
Mario Commodo ◽  
Gianluigi De Falco ◽  
Rosanna Larciprete ◽  
Andrea D'Anna
Keyword(s):  
Carbon Nanostructures ◽  
Functional Materials ◽  
Building Blocks ◽  
Spectroscopic Characterization ◽  
Molecular Compound ◽  
Force Microscopy ◽  
Atomic Force ◽  
Thin Carbon ◽  
On Line ◽  
20 Nm

ABSTRACTIn this work we produce atomically thin carbon nanostructures which have a disk-like shape when deposited on a substrate. These nanostructures have intermediate characteristics between a graphene island and a molecular compound and have the potentiality to be used either as they are, or to become building blocks for functional materials or to be manipulated and engineered into composite layered structures.The carbon nanostructures are produced in a premixed ethylene/air flame with a slight excess of fuel with respect to the stoichiometric value. The size distribution of the produced compounds in aerosol phase has been measured on line by means of a differential mobility analyzer (DMA) and topographic images of the structures deposited on mica disks were obtained by Atomic Force Microscopy. Raman spectroscopy and XPS have been used to characterize their structure and the electronic and optical properties were obtained combining on-line photoionization measurements with Cyclic Voltammetry, light absorption and photoluminescence.When deposited on the mica substrate the carbon compounds assume the shape of an atomically thin disk with in plane diameter of about 20 nm. Carbon nano-disks consist of a network of small aromatic island with in plane length, La, of about 1 nm. Raman spectra evidence a significant amount of disorder which is in a large part due to the quantum confinement in the aromatic islands. Nano-disks contain small percentage of sp3 and the O/C ratio is lower than 6%. They furthermore present interesting UV and visible photoluminescence properties.

Characterization and Optimization of The Tco/a-Si:H(,B) Interface for Solar Cells by In-Situ Ellipsometry and Sims/XPS Depth Profiling

1994 ◽  
Vol 336 ◽  
Author(s):  
H.N. Wanka ◽  
E. Lotter ◽  
M.B. Schubert
Keyword(s):  
Solar Cells ◽  
Light Trapping ◽  
Hydrogen Plasma ◽  
Depth Profiling ◽  
Trapping Efficiency ◽  
Force Microscopy ◽  
Hydrogen Plasmas ◽  
Atomic Force ◽  
20 Nm

ABSTRACTThe chemical reactions at the surface of transparent conductive oxides (SnO2, ITO and ZnO) have been studied in silane and hydrogen plasmas by in-situ ellipsometry and by SIMS as well as XPS depth profiling. SIMS and XPS of the interface reveal an increasing amount of metallic phases upon lowering a-Si:H growth rates (controlled by plasma power), indicating that the ion and radical impact is more than compensated by protecting the surface by a rapidly growing a-Si:H film. Hence, optical transmission of TCO films as well as the efficiency of solar cells can be improved if the first few nanometers of the p-layer are grown at higher rates. Comparing a-Si:H deposition on top of different TCOs, reduction effects on ITO and SnO2 have been detected whereas ZnO appeared to be chemically stable. Therefore an additional shielding of the SnO2 surface by a thin ZnO layer has been investigated in greater detail. Small amounts of H are detected close to the ZnO surface by SIMS after hydrogen plasma treatment, but no significant changes occur to the optical and electrical properties. In-situ ellipsometry indicates that a ZnO layer as thin as 20 nm completely protects SnO2 from being reduced to metallic phases. This provides for shielding of textured TCOs, and hence rising solar cell efficiencies, too. Regarding light trapping efficiency we additionally investigated the smoothing of initial TCO texture when growing a-Si:H on top by combining atomic force microscopy and spectroscopie ellipsometry.

SURFACE PLASMON ENHANCED OPTICAL SECOND HARMONIC GENERATION IN ULTRA-THIN METALLIC FILMS

1999 ◽  
Vol 08 (04) ◽  
pp. 503-518 ◽  
Author(s):  
JUH-TZENG LUE ◽  
CHIA-SHY CHANG
Keyword(s):  
Second Harmonic ◽  
Angular Position ◽  
Field Enhancement ◽  
Surface Scattering ◽  
Metallic Films ◽  
Silver Films ◽  
Force Microscopy ◽  
Atomic Force ◽  
Peak Intensity ◽  
20 Nm

Internal reflection of second-harmonic generations from silver films with thickness ranging from 5 nm to 50 nm are enhanced by the excitation of surface plasmons under Kretschmann configuration. Enhancement of the SHG was observed at a film thickness of 20 nm resulting from the field enhancement of granular structure. For thinner films, the surface reveals disconnected islands as inspected by the atomic force microscopy. The incident angular position to find the peak intensity and the change of linewidth of the SHG can almost satisfactorily be predicted by the theory based on surface scattering.

EX SITU ATOMIC FORCE MICROSCOPY STUDIES OF SURFACE MORPHOLOGY ON {001} FACES OF MMTWD CRYSTALS

2006 ◽  
Vol 13 (05) ◽  
pp. 607-611
Author(s):  
X. J. LIU ◽  
X. Q. WANG ◽  
Z. Y. WANG ◽  
D. XU ◽  
G. W. YU ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Atomic Force Microscopy ◽  
Surface Morphology ◽  
Temperature Stress ◽  
Growth Rates ◽  
High Density ◽  
Ex Situ ◽  
Force Microscopy ◽  
Elementary Steps ◽  
Atomic Force

Surface morphology of the {001} faces of MMTWD crystals grown from by the temperature-lowering method has been studied. Monolayer and multilayer steps elongate along the a direction, which is determined by the crystal structure. Apart from that, the elementary steps have narrower terraces than the bunched ones, which may be resulting from the faster growth rates of the former than the latter. The formation of the protuberances at the step fronts is primarily associated with the uneven growth rates. The hollow cavities also elongate along the a direction, which demonstrates that the formation of them is also restricted by the crystal structure. Cracks are supposed to occur during harvesting, handling, or temperature stress afterwards. Growth of the 3D hillocks in high density can probably cause large stress and induce structure mismatch and serious cracks at the later stage.

Macro- to nanoscale study of the effect of aqueous sulphate on calcite growth

2008 ◽  
Vol 72 (1) ◽  
pp. 141-144 ◽  
Author(s):  
A. I. Vavouraki ◽  
C. V. Putnis ◽  
A. Putnis ◽  
E. H. Oelkers ◽  
P. G. Koutsoukos
Keyword(s):  
Atomic Force Microscopy ◽  
Growth Rates ◽  
Kinetics And Mechanism ◽  
Two Dimensional ◽  
Mixed Flow ◽  
Flow Reactors ◽  
Force Microscopy ◽  
Atomic Force

AbstractCalcite growth rates were measured in the presence of sulphate using mixed-flow reactors and in situ Atomic Force Microscopy. Preliminary observations reveal that the kinetics and mechanism of the calcite growth was altered by the presence of sulphate. Calcite growth rates in the presence of sulphate (≥ mM) were decreased and two-dimensional nuclei tend to grow on top of existing nuclei, rather than spreading. The height of new nuclei was ~4 Å, 1 Å greater than that of pure calcite growth. This difference reflects the incorporation of tetrahedral SO2-4 anions into the calcite lattice.

Mechanical Stress, Grain-boundary Relaxation, and Oxidation of Sputtered CuNi(Mn) Films

1999 ◽  
Vol 14 (4) ◽  
pp. 1286-1294 ◽  
Author(s):  
W. Brückner ◽  
W. Pitschke ◽  
S. Baunack ◽  
J. Thomas
Keyword(s):  
Grain Boundary ◽  
Microstructural Characterization ◽  
Excess Vacancy ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Boundary Relaxation ◽  
20 Nm ◽  
Atomic Rearrangement

This paper focuses on understanding stress development in CuNi42Mn1 thin films during annealing in Ar. In addition to stress-temperature measurements, resistance-temperature investigations and chemical and microstructural characterization by Auger electron spectroscopy, scanning and transmission electron microscopy, x-ray diffraction, and atomic force microscopy were also carried out. The films are polycrystalline with a grain size of 20 nm up to 450 °C. To explain the stress evolution above 120 °C, atomic rearrangement (excess-vacancy annihilation, grain-boundary relaxation, and shrinkage of grain-boundary voids) and oxidation were considered. Grain-boundary relaxation was found to be the dominating process up to 250–300 °C. A sharp transition from compressive to tensile stress between 300 and 380 °C is explained by the formation of a NiO surface layer due to reaction with the remaining oxygen in the Ar atmosphere. This oxidation is masking the inherent structural relaxation above 300 °C.

Electro-Mechanical Coupling and Power Generation in a Pzt Micro-Engine

2001 ◽  
Vol 687 ◽  
Author(s):  
D.F. Bahr ◽  
K.R. Bruce ◽  
B.W. Olson ◽  
L.M. Eakins ◽  
C.D. Richards ◽  
...  
Keyword(s):  
Thin Film ◽  
Heat Engine ◽  
Carnot Cycle ◽  
Mechanical Coupling ◽  
Force Microscopy ◽  
Atomic Force ◽  
Pzt Film ◽  
Film Adhesion ◽  
Piezoelectric Thin Film ◽  
20 Nm

AbstractA piezoelectric thin film MEMS device for generating power from a novel heat engine which approaches a Carnot cycle has been developed. The structure of the underlying electrode and PZT thin film generator has been optimized for increased adhesion. Atomic force microscopy was used to track electrode grain size and roughness; generating grain sizes of approximately 100 and 200 nm in diameter and a roughness of about 14-20 nm provide substantial improvements in film adhesion over systems with smaller grains and smoother surfaces. This has led to the ability to operate the engine at frequencies between 10 and 1500 Hz. The system of interest (a fluid filled cavity sealed by a micromachined silicon membrane and the PZT film) shows increased deflections for a given pressure applied to the membrane at frequencies where the system resonates. By operating the system dynamically, it is possible to generate more than 2 V from a single generator structure.

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