Composition and Structure of Epitaxial CaF2 Layers at the First Stages of Their Growth on Si(111)

2001 ◽  
Vol 696 ◽  
Author(s):  
R. Würz ◽  
W. Bohne ◽  
W. Fuhs ◽  
J. Röhrich ◽  
M. Schmidt ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Film Growth ◽  
Stoichiometric Composition ◽  
Interface Reaction ◽  
Heavy Ion ◽  
Interface Layer ◽  
Buffer Layers ◽  
Ex Situ ◽  
Elastic Recoil ◽  
Detection Analysis

AbstractCaF2 films with thicknesses in the monolayer range (<20 Å) were grown on Si(111) by evaporation from a CaF2 source at UHV conditions. They were characterized ex-situ by Heavy-Ion Elastic Recoil Detection Analysis (HI-ERDA), RBS/Channeling, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The F/Ca ratio of the films was found to depend on the growth temperature Ts and to deviate appreciably from the stoichiometric composition (F/Ca=2). Due to an interface reaction which leads to a CaF-interface layer a change from polycrystalline to epitaxial growth occurs at Ts=450°C. At higher temperature film growth started with a closed layer of CaF on top of which CaF2 layers with an increasing fraction of pinholes were formed. By means of a two-step process at different temperatures, the amount of pinholes could be strongly reduced. It was found, that buffer layers of CaF2 with a CaF interface layer introduced in Au/p-Si contacts enhance the barrier height by as much as 0.36eV to values of 0.64eV.

A Study of Indium Nitride Films Grown Under Conditions Resulting in Apparent Band-gaps from 0.7 eV to 2.3 eV

2002 ◽  
Vol 743 ◽  
Author(s):  
K. S. A. Butcher ◽  
M. Wintrebert-Fouquet ◽  
Motlan ◽  
S. K. Shrestha ◽  
H. Timmers ◽  
...  
Keyword(s):  
Band Gap ◽  
Photoelectron Spectroscopy ◽  
Indium Nitride ◽  
Threshold Energy ◽  
Heavy Ion ◽  
Elastic Recoil ◽  
Elastic Recoil Detection ◽  
Detection Analysis ◽  
Direct Band ◽  
Band Tailing

ABSTRACTThe band-gap of indium nitride has long been believed to be about 1.9eV with slight variations due to band-tailing in polycrystalline samples and degenerate doping. Recently, other values as low as 0.7 eV have apparently been observed. We have compared samples spanning this apparent range of band-gap using secondary ion mass spectroscopy (SIMS), X-ray Photoelectron Spectroscopy (XPS) and heavy ion elastic recoil detection analysis (ERDA), in conjunction with spectral optical density measurements. Once structural inhomogeneiteies are taken into account, we show that much of the conflicting data are compatible with direct photoionisation with a threshold energy of about 1.0eV. This feature was first reported in polycrystalline indium nitride over 15 years ago and attributed to a ∣p> like defect state. We ask whether the feature may instead be a direct band-gap.

Nano-Structured Amorphous Carbon Films Synthesised Using Decr Plasma

2001 ◽  
Vol 675 ◽  
Author(s):  
André Golanski ◽  
Dieter Grambole ◽  
Jean Hommet ◽  
Folker Herrmann ◽  
Philippe Kern ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Electron Cyclotron Resonance ◽  
Plasma Reactor ◽  
Argon Plasma ◽  
Carbon Films ◽  
Plasma Pressure ◽  
Nuclear Reaction Analysis ◽  
Elastic Recoil ◽  
Si Substrates ◽  
Detection Analysis

ABSTRACTA Distributed Electron Cyclotron Resonance plasma reactor powered by a microwave generator operating at 2.45 GHz was used to deposit ta-C:H (Diamond-Like Carbon, DLC) thin films at RT. A graphite sputtering target immersed in an argon plasma was used as carbon source. The Ar plasma density was about 5×1010 cm-3. Single crystal <100> Si substrates were RF biased to a negative voltage of -80 V. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), nuclear reaction analysis (NRA) using the resonance at 6.385 MeV of the reaction: 15N + 1H-→ 12C + 4He + γ, elastic recoil detection analysis (ERDA) and Rutherford backscattering (RBS) were used to investigate the early phase of the growth. The morphology of the films grown at low pressure (0.3 mTorr) is shown to be dominated by stress-mediated nucleation leading to formation of basket-like clusters of circular hillocks 20 nm high surrounded by a planar, mostly sp2 bonded film ∼8 nm thick. With increasing plasma pressure the spatial frequency of the hillocks becomes random and the growth is dominated by the Stranski-Krastanov mode. The XPS data taken at decreasing emergence angles show that the structure of the hillocks is dominated by sp3 bonded carbon. The XPS argon signal disappears at 10° emergence angle indicating that integration of argon occurs mainly within the sp bonded regions. The NRA and ERDA analysis show that the amount of integrated hydrogen decreases with increasing substrate current density. RBS data indicate that increasing bias enhances argon integration.

Heavy ion elastic recoil detection analysis set up for electronic sputtering studies

2006 ◽  
Vol 161 (4) ◽  
pp. 247-255 ◽  
Author(s):  
S. Ghosh ◽  
D. K. Avasthi ◽  
A. Tripathi ◽  
D. Kabiraj ◽  
P. Sugathan ◽  
...  
Keyword(s):  
Heavy Ion ◽  
Elastic Recoil ◽  
Elastic Recoil Detection Analysis ◽  
Elastic Recoil Detection ◽  
Detection Analysis ◽  
Set Up

Hydrogen Evolution and Interface Reaction of Cu Thin Film on a-Si:H

1993 ◽  
Vol 311 ◽  
Author(s):  
L. Bemardino ◽  
Carlos Achete ◽  
F. L. Freire
Keyword(s):  
Low Temperature ◽  
Sheet Resistance ◽  
Interface Reaction ◽  
Elastic Recoil ◽  
Elastic Recoil Detection ◽  
Detection Analysis ◽  
Rf Glow Discharge ◽  
Cu Thin Film ◽  
Effusion Method

ABSTRACTThe Cu/a-Si:H system has been studied by gas effusion method, elastic recoil detection analysis (ERDA), in situ sheet resistance measurements and scanning electron microscopy. Cu layers of 15 and 90 nm in thickness were deposited by e-beam evaporation onto 1 μm a-Si:H films produced by RF glow discharge on Si(100) substrates at 250 °C. The most important effects are observed in the effusion measurements, when pure a-Si:H samples and Cu/a-Si:H samples are compared. For the Cu/a-Si:H samples, three well-defined peaks are observed, one at very low temperature (T=200 °C), another at 380 °C and a high temperature peak at about. However, pure a-Si:H shows only one effusion maxima at 550 °C. The low temperature effusion peaks are directly correlated with steps increases in the sheet resistance measurements. The first one (T=200 °C) is due to the beginning of silicide formation. The H2 evolution at 380 °C is correlated to phase transition in the a-Si:H film. The hydrogen depth profiles obtained by ERDA and SEM observations are also used to describe the aspects of the Cu/a-Si:H interaction.

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