Novel in situ and real-time optical probes to detect (surface) defect states of a-Si:H

AbstractThis paper describes two novel optical diagnostics that were recently introduced to the field of Si-based thin films, in particular for probing defect states present in the bulk and at the surface of a-Si:H films. It is expected that these diagnostics, when applied in situ or real time during film growth, can provide new insights into the a-Si:H film properties as well as into the fundamental surface processes during growth. The first method is cavity ringdown spectroscopy (CRDS). From ex situ measurements on a-Si:H thin films, it is shown that this method is very powerful for measuring absolute defect-related absorptions at subgap energies without the need for a calibration procedure, even for films as thin as 4 nm. It is also shown that the method can be used for measuring rare-earth dopants – here Er3+ in silicon-rich oxide – to the extent that issues about absorption cross-sections can be resolved by using thin samples instead of waveguides. Furthermore, the in situ application of the method for thin films is discussed by presenting the evanescent-wave cavity ringdown (EW-CRDS) technique. The second method is spectroscopic second harmonic generation (SHG). It has been found that this non-linear optical technique yields a photon energy dependent signal for as-deposited a-Si:H films and that this signal has a contribution from a-Si:H surface states. From a comparison with c-Si surface science studies, the possible origin of the signal from surface Si dangling bonds and strained Si-Si bonds is discussed. The application of SHG during real-time film growth is also presented.

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Thin film stress and microstructure analysis by energy-dispersive diffraction

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314092754 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C724-C724

Author(s):

Christoph Genzel

Keyword(s):

Thin Film ◽

Thin Films ◽

Residual Stress ◽

Film Growth ◽

High Energy ◽

Energy Dispersive ◽

Film Stress ◽

Ex Situ ◽

Near Surface

The most important advantage of energy dispersive (ED) diffraction compared with angle dispersive methods is that the former provides complete diffraction patterns in fixed but arbitrarily selectable scattering directions. Furthermore, in experiments that are carried out in reflection geometry, the different photon energies E(hkl) of the diffraction lines in an ED diffraction pattern can be taken as an additional parameter to analyze depth gradients of structural properties in the materials near surface region. For data evaluation advantageous use can be made of whole pattern methods such as the Rietveld method, which allows for line profile analysis to study size and strain broadening [1] or for the refinement of models that describe the residual stress depth distribution [2]. Concerning polycrystalline thin films, the features of ED diffraction mentioned above can be applied to study residual stresses, texture and the microstructure either in ex-situ experiments or in-situ to monitor, for example, the chemical reaction pathway during film growth [3]. The main objective of this talk is to demonstrate that (contrary to a widespread opinion) high energy synchrotron radiation and thin film analysis may fit together. The corresponding experiments were performed on the materials science beamline EDDI at BESSY II which is one of the very few instruments worldwide that is especially dedicated to ED diffraction. On the basis of selected examples it will be shown that specially tailored experimental setups allow for residual stress depth profiling even in thin films and multilayer coatings as well as for fast in situ studies of film stress and microstructure evolution during film growth.

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Mapping the Phase-Change Parameter Space of Hot-Wire CVD Si:H Films Using In-Situ Real Time Spectroscopic Ellipsometry

MRS Proceedings ◽

10.1557/proc-715-a25.2 ◽

2002 ◽

Vol 715 ◽

Cited By ~ 1

Author(s):

Dean H. Levi ◽

Brent P. Nelson ◽

John D. Perkins

Keyword(s):

Surface Roughness ◽

Real Time ◽

Parameter Space ◽

Spectroscopic Ellipsometry ◽

Film Growth ◽

Growth Parameter ◽

Ex Situ ◽

Degree Of Crystallinity ◽

Hot Wire

AbstractIn-situ real-time spectroscopic ellipsometry (RTSE) provides detailed information on the evolution of the structural and optical properties of Si:H films during film growth. We have used in-situ RTSE to characterize the film morphology and crystallinity of hot-wire CVD (HWCVD) Si:H films as a function of hydrogen dilution R=[H]/[H+SiH4], substrate temperature Ts, and film thickness db. Transitions from one mode of film growth to another are indicated by abrupt changes in the magnitude of the surface roughness during film growth. The degree of crystallinity of the film can be determined from the bulk dielectric function. We have studied the growth parameter space consisting of R from 0 to 12, Ts from 150°C to 550°C, and db from 0 to 1 um. For each set of R and Ts values, the structural evolution of the film can be characterized by the shape of the surface roughness thickness ds versus bulk thickness db curve. In contrast to studies done by Collins et al on PECVD growth of Si:H films, our studies of HWCVD growth find no conditions where ds remains constant after coalescence of the initial nucleation centers. Most of the films grown within the range of parameters studied exhibit a secondary nucleation and coalescence signature. The transition between a-Si:H and uc-Si:H growth is near the R=3 to R=4 dividing line. Initial coalescence of purely uc-Si:H material doesn't occur until R>8. We have verified the RTsE crystallinity classification using ex-situ Raman scattering.

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Real Time Ellipsometric Study of Boron Nitride Thin Film Growth

MRS Proceedings ◽

10.1557/proc-410-307 ◽

1995 ◽

Vol 410 ◽

Cited By ~ 1

Author(s):

E. Bertran ◽

A. Canillas ◽

J. Campmany ◽

M. El Kasmi ◽

E. Pascual ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Refractive Index ◽

Boron Nitride ◽

Real Time ◽

Film Growth ◽

Thin Film Growth ◽

Si Substrates ◽

Rf Glow Discharge

ABSTRACTWe present an in situ study of the growth of boron nitride thin films by real time ellipsometry. Films were produced in a PECVD reactor by rf glow discharge decomposition of ammonia (pure) and diborane (1% in hydrogen), on Ni-Cr coated c-Si substrates placed either on the powered electrode or on the grounded electrode of the reactor. A fast phase-modulated ellipsometer performed the real time monitoring of the growth processes at 350 nm. The ellipsometric angle trayectories were obtained through an autocalibrated method, especially suitable for the in situ optical analysis of transparent thin films. We applied several thin film growth optical models (homogeneous, two-layer, surface roughness) to analyze parameters of the films such as refractive index, extinction coefficient, roughness and deposition rate. In all the cases studied, the two-layer model fits well with the ellipsometric measurements, but a more sofisticated model considering a variable refractive index could better describe these films.

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Electronic and structural properties of copper selenide (Cu2−xSe) thin films as determined by in-situ real-time and ex-situ characterization

2012 38th IEEE Photovoltaic Specialists Conference ◽

10.1109/pvsc.2012.6317647 ◽

2012 ◽

Cited By ~ 1

Author(s):

H. Khatri ◽

K. Aryal ◽

R.W Collins ◽

S. Marsillac

Keyword(s):

Thin Films ◽

Real Time ◽

Structural Properties ◽

Copper Selenide ◽

Ex Situ ◽

Electronic And Structural Properties

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Studies of thin‐film growth, adsorption, and oxidation by in situ, real‐time, and ex situ ion beam analysis

Journal of Vacuum Science & Technology A Vacuum Surfaces and Films ◽

10.1116/1.579355 ◽

1994 ◽

Vol 12 (4) ◽

pp. 1557-1564 ◽

Cited By ~ 18

Author(s):

Yuping Lin ◽

A. R. Krauss ◽

O. Auciello ◽

Y. Nishino ◽

D. M. Gruen ◽

...

Keyword(s):

Thin Film ◽

Real Time ◽

Film Growth ◽

Ion Beam ◽

Thin Film Growth ◽

Ex Situ ◽

Ion Beam Analysis ◽

Beam Analysis

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Formation of Nickel Ferrite Films by Solid-State Reaction

Microscopy and Microanalysis ◽

10.1017/s1431927600010588 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 739-740

Author(s):

Matthew T. Johnson ◽

Paul G. Kotula ◽

C. Barry Carter

Keyword(s):

Thin Films ◽

Solid State ◽

Solid State Reaction ◽

Nickel Ferrite ◽

Elevated Temperatures ◽

Film Growth ◽

Ex Situ ◽

First Case ◽

Morphological Differences

Nickel ferrite (NiFe2O4) thin films are of potential interest for magnetic applications. In the present study, the production of NiFe2O4 by solid-state reaction between thin films of hematite (α-Fe2O3) and nickel oxide (NiO) on (0001) sapphire (α-Fe2O3) substrates has been examined. The NiFe2O4 thin films were prepared by two different methods. In the first case the NiFe2O4film was grown in situ in the deposition system, while in the second case the NiFe2O4 film was formed ex situ by reacting at elevated temperatures in air. These two methods of reaction lead to interesting morphological differences in the ferrite layers.Epilayers of α-Fe2O3 followed by NiO were deposited onto (0001) α-Al2O3 by pulsed-laser deposition (PLD) in 6 mTorr O2. NiFe2O4 films were obtained by reacting the starting films in two different ways: in situ (during film growth) and ex situ.. In both cases, the α-Fe2O3 films were grown under the same conditions while those for the deposition of the NiO layers were different.

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The use of transmission and analytical electron microscopy in studying reactions and phase transformations in thin film

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150046 ◽

1993 ◽

Vol 51 ◽

pp. 842-843

Author(s):

K. Barmak

Keyword(s):

Thin Film ◽

Thin Films ◽

Phase Transformations ◽

Analytical Electron Microscopy ◽

Ex Situ ◽

Multilayer Thin Films ◽

Absolute Concentration ◽

Analytical Electron ◽

Deposition Step

Generally, processing of thin films involves several annealing steps in addition to the deposition step. During the annealing steps, diffusion, transformations and reactions take place. In this paper, examples of the use of TEM and AEM for ex situ and in situ studies of reactions and phase transformations in thin films will be presented.The ex situ studies were carried out on Nb/Al multilayer thin films annealed to different stages of reaction. Figure 1 shows a multilayer with dNb = 383 and dAl = 117 nm annealed at 750°C for 4 hours. As can be seen in the micrograph, there are four phases, Nb/Nb3-xAl/Nb2-xAl/NbAl3, present in the film at this stage of the reaction. The composition of each of the four regions marked 1-4 was obtained by EDX analysis. The absolute concentration in each region could not be determined due to the lack of thickness and geometry parameters that were required to make the necessary absorption and fluorescence corrections.

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Real-Time Analysis Of In-Situ Spectroscopic Ellipsometric Data During Mbe Growth Of III-V Semiconductors

MRS Proceedings ◽

10.1557/proc-222-75 ◽

1991 ◽

Vol 222 ◽

Cited By ~ 10

Author(s):

B. Johs ◽

J. L. Edwards ◽

K. T. Shiralagi ◽

R. Droopad ◽

K. Y. Choi ◽

...

Keyword(s):

Real Time ◽

Optical Constants ◽

Growth Parameters ◽

Ex Situ ◽

Time Analysis ◽

Mbe Growth ◽

In Situ Data ◽

Real Time Analysis

ABSTRACTA modular spectroscopic ellipsometer, capable of both in-situ and ex-situ operation, has been used to measure important growth parameters of GaAs/AIGaAs structures. The ex-situ measurements provided layer thicknesses and compositions of the grown structures. In-situ ellipsometric measurements allowed the determination of growth rates, layer thicknesses, and high temperature optical constants. By performing a regression analysis of the in-situ data in real-time, the thickness and composition of an AIGaAs layer were extracted during the MBE growth of the structure.

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