scholarly journals Theoretical Analysis of Experimental Data of Sodium Diffusion in Oxidized Molybdenum Thin Films

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2479
Author(s):  
Orlando Ayala ◽  
Benjamin Belfore ◽  
Tasnuva Ashrafee ◽  
John Akwari ◽  
Grace Rajan ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Theoretical Analysis ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Substrate Temperature ◽  
Hole Transport ◽  
Growth Speed ◽  
Geometrical Shape ◽  
Sodium Diffusion

In this work, the diffusion process of sodium (Na) in molybdenum (Mo) thin films while it was deposited on soda lime glass (SLG) was studied. A small amount of oxygen was present in the chamber while the direct-current (DC) magnetron sputtering was used for the deposition. The substrate temperatures were varied to observe its effect. Such molybdenum films, with or without oxidations, are often used in thin film solar cells, either as back contact or as hole transport layers. Secondary ion mass spectrometry (SIMS) was used to quantify the concentration of the species. A grain diffusion mechanistic model incorporating the effect of grain and grain boundary geometrical shape and size was developed. The model was used to provide an in-depth theoretical analysis of the sodium diffusion in molybdenum thin films that lead to the measured SIMS data. It was observed that not only diffusion coefficients should be considered when analyzing diffusion processes in thin films but also the ratio of grain boundary size to grain size. Both depend on substrate temperature and directly affect the amount of diffused species in the film. The data were analyzed under the light of the film growth speed versus diffusion front speed, the effect of oxygen content, and the effect of substrate temperature on the overall diffusion process. The temperature inversely affects the ratio of grain boundary size and grain size and directly affects the diffusion coefficient, which leads to a preferable temperature at which the highest amount of alkali can be found in the film.

Texture Evolution of Lithium Fluoride Thin Films by Nucleation

2006 ◽  
Vol 979 ◽  
Author(s):  
Hakkwan Kim ◽  
Alexander H. King
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Substrate Temperature ◽  
Lithium Fluoride ◽  
Texture Evolution ◽  
Dark Field ◽  
Acceptable Error ◽  
Annealing Conditions ◽  
Surface Normal ◽  
Transmission Electron

AbstractWe have used a transmission electron microscope (TEM)-based method to extract grain size information for 〈111〉 surface normal grains in lithium fluoride (LiF) thin films, and applied this to analyze textures as a function of substrate temperature and annealing time. The size distributions of grains diffracting into the (111)+(200) and (220) rings were measured separately using dark field (DF) TEM images. From these data, we deduce the distribution of 〈111〉 surface normal grain sizes based on the assumption that only 3 principal textures (100), (110) and (111) exist in films. The (111) texture formation was also observed by x-ray diffraction (XRD). For all deposition and annealing conditions, the grain size data can be matched to lognormal distributions within an acceptable error, but at longer annealing times the distribution becomes bimodal. A novel feature of the LiF films is that the (111) texture component strengthens with annealing and substrate temperature, through the nucleation of new grains rather than the growth of existing ones.

EFFECT OF SUBSTRATE TEMPERATURE ON THE STRUCTURAL AND OPTICAL PROPERTIES OF NiTsPc THIN FILMS

2019 ◽  
Vol 27 (03) ◽  
pp. 1950124 ◽  
Author(s):  
MOHAMMED YARUB HANI ◽  
ADDNAN H. AL-AARAJIY ◽  
AHMED M. ABDUL-LETTIF
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Optical Properties ◽  
Substrate Temperature ◽  
Energy Gap ◽  
Chemical Spray Pyrolysis ◽  
Structural And Optical Properties ◽  
Absorption Bands ◽  
Tauc Plot ◽  
Substrate Temperatures

Nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (NiTsPc) thin films were deposited on glass substrates at different substrate temperatures ([Formula: see text]) by chemical spray pyrolysis (CSP) technique. The substrate temperature varied from 110∘C to 310∘C in 50∘C steps. The substrate surface temperature is the main parameter that determines the film morphology and properties of the thin films. The structural properties of the deposited NiTsPc thin films were investigated by X-ray diffraction (XRD) and from the obtained results, it was shown that depositing thin films using 210∘C as [Formula: see text] results in higher crystallinity. Atomic force microscope (AFM) was employed to obtain the surface topography and to calculate the roughness and grain size. The smoothest thin film surface was obtained when using at 160∘C, while the highest roughness was obtained at 310∘C. The optical properties were investigated by ultraviolet visible (UV-Vis) spectrophotometer and fluorescence spectrophotometer. From the absorption spectra recorded in the wavelength range 190–1100[Formula: see text]nm, two absorption bands were observed, which are known as Soret and Q-band. By observing the absorption spectrum, it can be concluded that the deposited thin films at 110∘C–310∘C have direct energy gap. From Tauc plot relation, the energy gap ([Formula: see text]) was calculated. The values of the energy gap were between 3.05 and 3.14[Formula: see text]eV. It was observed that different [Formula: see text] highly affects the structural and optical properties of the deposited thin films. The crystallinity, grain size, roughness and the optical properties were strongly affected by the different substrate temperatures.

A Re-Appraisal of Cavity Growth Processes in Superplasticity

1990 ◽  
Vol 196 ◽  
Author(s):  
Yan Ma ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Superplastic Deformation ◽  
Cavity Growth ◽  
Normal Model ◽  
Experimental Conditions ◽  
Diffusion Growth ◽  
New Model

ABSTRACTIt is well known that cavities are nucleated and grow during the superplastic deformation of many materials. The various theories for cavity growth are examined with special emphasis on the role of growth by diffusion. It is demonstrated that the normal model for the diffusion growth of cavities is inadequate for superplastic materials when the grain boundary lengths are very small. By developing a new model for the growth of an isolated cavity to sizes exceeding the grain size, it is shown that the diffusion process may play a major role in cavity growth under a range of experimental conditions.

Constrained Grain Boundary Diffusion In Thin Copper Films

2004 ◽  
Vol 821 ◽  
Author(s):  
Markus J. Buehler ◽  
Alexander Hartmaier ◽  
Huajian Gao
Keyword(s):  
Thin Films ◽  
Theoretical Analysis ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Atomic Scale ◽  
Diffusional Creep ◽  
Copper Films ◽  
And Diffusion

AbstractIn a recent study of diffusional creep in polycrystalline thin films deposited on substrates, we have discovered a new class of defects called the grain boundary diffusion wedges (Gao et al., Acta Mat. 47, pp. 2865-2878, 1999). These diffusion wedges are formed by stress driven mass transport between the free surface of the film and the grain boundaries during the process of substrate-constrained grain boundary diffusion. The mathematical modeling involves solution of integro-differential equations representing a strong coupling between elasticity and diffusion. The solution can be decomposed into diffusional eigenmodes reminiscent of crack-like opening displacement along the grain boundary which leads to a singular stress field at the root of the grain boundary. We find that the theoretical analysis successfully explains the difference between the mechanical behaviors of passivated and unpassivated copper films during thermal cycling on a silicon substrate. An important implication of our theoretical analysis is that dislocations with Burgers vector parallel to the interface can be nucleated at the root of the grain boundary. This is a new dislocation mechanism in thin films which contrasts to the well known Mathews-Freund-Nix mechanism of threading dislocation propagation. Recent TEM experiments at the Max Planck Institute for Metals Research have shown that, while threading dislocations dominate in passivated metal films, parallel glide dislocations begin to dominate in unpassivated copper films with thickness below 400 nm. This is consistent with our theoretical predictions. We have developed large scale molecular dynamics simulations of grain boundary diffusion wedges to clarify the nucleation mechanisms of parallel glide in thin films. Such atomic scale simulations of thin film diffusion not only show results which are consistent with both continuum theoretical and experimental studies, but also revealed the atomic processes of dislocation nucleation, climb, glide and storage in grain boundaries. The study should have far reaching implications for modeling deformation and diffusion in micro- and nanostructured materials.

Characterization of Sputtered CdTe Thin Films with Electron Backscatter Diffraction and Correlation with Device Performance

2015 ◽  
Vol 21 (4) ◽  
pp. 927-935 ◽  
Author(s):  
Matthew M. Nowell ◽  
Michael A. Scarpulla ◽  
Naba R. Paudel ◽  
Kristopher A. Wieland ◽  
Alvin D. Compaan ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Backscatter Diffraction ◽  
Electrical Performance ◽  
Poor Correlation ◽  
Twin Boundaries ◽  
Electron Backscatter ◽  
Backscatter Diffraction

AbstractThe performance of polycrystalline CdTe photovoltaic thin films is expected to depend on the grain boundary density and corresponding grain size of the film microstructure. However, the electrical performance of grain boundaries within these films is not well understood, and can be beneficial, harmful, or neutral in terms of film performance. Electron backscatter diffraction has been used to characterize the grain size, grain boundary structure, and crystallographic texture of sputtered CdTe at varying deposition pressures before and after CdCl2 treatment in order to correlate performance with microstructure. Weak fiber textures were observed in the as-deposited films, with (111) textures present at lower deposition pressures and (110) textures observed at higher deposition pressures. The CdCl2-treated samples exhibited significant grain recrystallization with a high fraction of twin boundaries. Good correlation of solar cell efficiency was observed with twin-corrected grain size while poor correlation was found if the twin boundaries were considered as grain boundaries in the grain size determination. This implies that the twin boundaries are neutral with respect to recombination and carrier transport.

Effects Of Grain Boundaries on the Resistivity of Cosputtered Wsi2 Films

1981 ◽  
Vol 10 ◽  
Author(s):  
D. R. Campbell ◽  
S. Mader ◽  
W. K. Chu
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Reflection Coefficient ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Charge Carriers ◽  
Boundary Scattering ◽  
Grain Boundary Scattering

ABSTRACTResistivity and grain size measurements on thin films of co-sputtered WSi2 show that the resistivity in this material is dominated by grain boundary scattering. The reflection coefficient for the transport of charge carriers through the grain boundaries was determined to be approximately 0.9.

Theoretical Calculation for the Young's Modulus of Poly-Si and a-Si Films

1992 ◽  
Vol 276 ◽  
Author(s):  
Shuwen Guo ◽  
Daowen Zou ◽  
Weiyuan Wang
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Grain Size ◽  
Grain Boundary ◽  
Theoretical Calculation ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Boundary Effects ◽  
Wide Range ◽  
Si Films

ABSTRACTA newly theoretical calculation for the Young's modulus Ey of poly-Si and a-Si thin films based on the combination of grain and grain boundary effects as well as the dependance of crystalline orientations is presented. The calculated results are in agreement with the experimental results in a wide range of grain size and hydrogen concentrations published in the literatures. The reason for aberration among experimental data of poly-Si and a-Si films caused by different hydrogen concentrations, texture and grain size has been discussed. The results offer a better understanding of. the effects of film structures on elastic properties of poly-Si and a-Si films.

Growth of Large Crystalline Grain Al Thin Films on Amorphous Substrates

1985 ◽  
Vol 54 ◽  
Author(s):  
G. Sberveglieri ◽  
V. Canevari ◽  
N. Romeo ◽  
C. Spaggiari
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Melting Point ◽  
Substrate Temperature ◽  
Liquid Nitrogen Temperature ◽  
Maximum Temperature ◽  
Glass Substrates ◽  
Amorphous Substrates ◽  
Columnar Grains ◽  
Computer Controlled

ABSTRACT(111) uniquely oriented large crystalline grain Al thin films have been grown on amorphous substrates such as glass or fused quartz. Al has been evaporated by means of an electron beam in a vacuum of 10-7 mbar which was obtained by a conventional oil diffusion pump in conjunction with a titanium sublimation pump and a series of shields cooled at the liquid nitrogen temperature. By studying the variation of the grain size as a function of the growth temperature, a large increase in the grain size has been found at a substrate temperature 100°C below the Al melting point. This has been interpreted as due to the beginning of the metal surface melting and, as a consequence, to the quasi rheotaxial growth of the metal on itself. When the growth has been carried out at a substrate temperature close to the Al melting point (625°C), the grain size has been found out to increase exponentially as a function of the film thickness with a slope which slows down at a thickness of about 1 pm. (111) oriented columnar grains with a size of 50 – 100 pm, hitherto unreported, have been obtained on glass substrates kept at a maximum temperature of 655 °C. The surface morphology of the Al films has been studied by SEM microscopy while the film structural properties have been studied by an X-ray powder-diffracto-meter and by computer - controlled pole figure goniometer.

Morphological and Structural Study of Nanostructured Tin Dioxide (SnO2) Thin Films by Spray Pyrolysis

2012 ◽  
Vol 626 ◽  
pp. 672-676
Author(s):  
Boon Hoong Ong ◽  
Heng Choy Lee ◽  
Sharifah Bee Abdul Hamid
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Substrate Temperature ◽  
Spray Pyrolysis ◽  
Tin Dioxide ◽  
Spray Pyrolysis Technique ◽  
Chemical Spray Pyrolysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chemical Spray

Nanostructured SnO2 thin films were deposited on glass substrate using chemical spray pyrolysis technique. Three influent synthesis parameters, namely (i) the precursor concentration (0.2M and 0.5M), (ii) the substrate temperature (250°C and 350°C) and (iii) doping with zinc (Zn) were investigated in term of their effects on the morphology and structure of SnO2 thin films. These films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectrometry (EDX) techniques. The grain size of the films was observed to increase as the concentration of the precursors is increased. Substrate temperature is proved to be crucial in determining the crystallinity of the films as the films are reported to grow at temperature above 270°C. Besides, the addition of dopant was found to reduce the grain size of the film.

scholarly journals Morphology and Electron Emission Properties of Nanocrystalline CVD Diamond Thin Films

1997 ◽  
Vol 495 ◽  
Author(s):  
Alan R. Krauss ◽  
Dieter M. Gruen ◽  
Daniel Zhou ◽  
Thomas G. Mccauley ◽  
Lu Chang Qin ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Hydrogen Concentration ◽  
Electron Emission ◽  
Microwave Plasma ◽  
Initial Growth ◽  
Average Grain Size ◽  
Diamond Thin Films

ABSTRACTNanocrystalline diamond thin films have been produced by microwave plasma-enhanced chemical vapor deposition (MPECVD) using C60/Ar/H2 or CH4/Ar/H2 plasmas. Films grown with H2 concentration ≤ 20% are nanocrystalline, with atomically abrupt grain boundaries and without observable graphitic or amorphous carbon phases. The growth and morphology of these films are controlled via a high nucleation rate resulting from low hydrogen concentration in the plasma. Initial growth is in the form of diamond, which is the thermodynamic equilibrium phase for grains < 5 nm in diameter. Once formed, the diamond phase persists for grains up to at least 15–20 nm in diameter. The renucleation rate in the near-absence of atomic hydrogen is very high (∼1010 cm2sec−1), limiting the average grain size to a nearly constant value as the film thickness increases, although the average grain size increases as hydrogen is added to the plasma. For hydrogen concentrations less than ∼20%, the growth species is believed to be the carbon dimer, C2, rather than the CH3* growth species associated with diamond film growth at higher hydrogen concentrations. For very thin films grown from the C60 precursor, the threshold field (2 to ∼60 volts/micron) for cold cathode electron emission depends on the electrical conductivity and on the surface topography, which in turn depends on the hydrogen concentration in the plasma. A model of electron emission, based on quantum well effects at the grain boundaries is presented. This model predicts promotion of the electrons at the grain boundary to the conduction band of diamond for a grain boundary width ∼3–4 Å, a value within the range observed by TEM.

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