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Category :
Languages : en
Pages :
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The effects of deposition temperature and in-situ post-deposition annealing on the microstructure of coevaporated Cu(InGa)Se2 thin films and on the performance of the resulting solar cell devices have been characterized. Films were deposited at substrate temperatures of 150°C, 300°C and 400°C. Films were also deposited at these temperatures and then annealed in-situ at 550°C for 10 minutes. In as -deposited films without annealing, additional XRD reflections that may be due to a polytypic modification of the chalcopyrite phase were observed. Films deposited at 150°C were Se-rich. Post-deposition annealing caused microstructural changes in all films and improved the resulting solar cells. Only films deposited at 400°C, however, yielded high-efficiency devices after post-deposition annealing that were equivalent to devices made from films grown at 550°C. Films originally deposited at 300°C yielded devices after post-deposition annealing with VOC close to that of devices made from films grown at 550°C, despite smaller grain size.
Author: Michael Christopher Johnson
Publisher:
ISBN:
Category : Aluminum nitride
Languages : en
Pages : 370
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Author:
Publisher:
ISBN:
Category : Electrical engineering
Languages : en
Pages : 2304
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Author: L. Holland
Publisher:
ISBN:
Category : Vapor-plating
Languages : en
Pages : 608
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Author: P. Joshi
Publisher: The Electrochemical Society
ISBN: 1566777259
Category : Science
Languages : en
Pages : 63
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The papers included in this issue of ECS Transactions were originally presented in the symposium ¿Novel Plasma Techniques for Low Temperature Processing of Thin Films for Flexible Electronics¿, held during the 215th meeting of The Electrochemical Society, in San Francisco, California from May 24 to 29, 2009.
Author: Kai-Ann Yang
Publisher:
ISBN:
Category :
Languages : en
Pages : 368
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Author: Guangneng Zhang
Publisher: ProQuest
ISBN: 9780549716440
Category : Ceramic materials
Languages : en
Pages : 384
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Ceramic thin films have received substantial interest and found numerous applications. A novel ceramic thin films deposition technique has been developed and studied systematically. This technique employs controlled hydrolysis of inorganic salt as precursor from aqueous solutions at low temperature. It starts with the nucleation followed by growth of the particles. The nucleation can take place through homogeneous or heterogeneous nucleation. One of the determining parameters seems to the degree of supersaturation, which is the thermodynamic driving force for nucleation. In light of this, our work first focused on the definition and calculation of degree of supersaturation, and our experiments then indicated the role of degree of supersaturation in nucleation and growth and further deposition processes. We found that homogeneous nucleation is prevalence when degree of supersaturation is high enough, while heterogeneous nucleation can play a more important role when degree of supersaturation is low enough. The growing film can avoid lattice strain between different microstructures. It seems that the preference toward either of the two mechanisms results in distinct film microstructures and morphologies. This diversity introduced two more research areas, one in modeling of intermolecular forces, and the other in film properties. Specifically, we have studied the deposition of ZrO2, TiO2, and SnO2 thin films on various substrates including bare Si and self-assembled monolayer (SAM)-coated Si substrates. We found that all the films can be deposited on both substrates. In addition, we found the TiO2 films display a large variety of morphologies, from very dense particulate structure to dendritic structure, due to different degrees of supersaturation. From classic nucleation theory and experiments, we determined the interfacial energy and critical nuclei diameter for nucleation of TiO2 to be 0.072 J·m-2 and typically 0.5 nm, respectively. We developed a quantitative approach to employ the DLVO theory to explain deposition behaviors and provide theoretical guideline for material design. Dynamic nanoindentations suggested moduli of TiO2, ZrO2 and SnO2 films were 27.95, 21.72, and 11.94 GPa, respectively. Dye penetration test indicated great potential of TiO2 films in hermetic package. Refractive index of the as-deposited TiO2 films was 1.7824±0.0172 (at 590.44 nm) determined by ellipsometry.
Author: Cen, Xi
Publisher:
ISBN: 9780355151527
Category :
Languages : en
Pages :
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Thin films deposited at low temperatures are often kinetically constrained and will dewet the underlying substrate when annealed. Solid state dewetting is driven by the minimization of the total free energy of thin film-substrate interface and free surface, and mostly occurs through surface diffusion. Dewetting is a serious concern in microelectronics reliability. However, it can also be utilized for the self-assembly of nanostructures with potentials in storage, catalysis, or transistors. Therefore, a fundamental understanding of the dewetting behavior of thin metal films is critical for improving the thermal stability of microelectronics and controlling the order of self-assembled nanostructures. Mechanisms for dewetting of single layer films have been studied extensively. However little work has been reported on multilayer or alloyed thin films. In the thesis, the solid state dewetting of Au/Ni bilayer films deposited on SiO2/Si substrates was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and aberration corrected scanning TEM (STEM). Ex-situ SEM and TEM studies were performed with in-situ TEM heating characterization to identify the mechanisms during the dewetting process of Au/Ni bilayer films. The solid state dewetting of Au/Ni bilayer films from SiO2/Si substrates exhibits both homogeneous and localized dewetting of Ni and long-edge retraction for Au under isothermal annealing condition. The top Au layer retracts up to 1 mm from the edge of the substrate wafer to reduce the energetically unfavored Au/Ni interface. In contrast, Ni dewets and agglomerates locally due to its limited diffusivity compared to Au. Film morphology and local chemical composition varies significantly across hundreds of microns along the direction normal to the retracting edge. Besides long range edge receding, localized dewetting shows significant changes in film morphology and chemical distribution. Both Au and Ni shows texturing. Despite the initial deposition sequence of the as-deposited Au/Ni/SiO2/Si interface structure, the majority of the metal/SiO2 interface is Au/SiO2 after annealing at 675°C for 1 hour. Cross-Sectional TEM revealed that void nucleation is predominantly observed at Au/Ni/SiO2 triple junctions, rather than grain boundary grooving at free surface of the metal film. The formation of Au/SiO2 interface sections is found to be energetically preferred over Ni/SiO2 due to compressive stress in the as-deposited Ni layer. In-situ cross-sectional TEM heating studies demonstrate that the dewetting transition initiates at 400°C. Au diffuses through Ni grain boundaries towards the underlying Ni layer and forms more energetically favorable Au/SiO2 interface. The adsorption of Au along Ni grain boundaries, NiO[subscript x]/Ni and SiO2/Ni phase boundaries is observed to lower the interfacial energy. The experimental observations suggest that alloying, unequal self-diffusion coefficient and metal/metal interface strongly affect the bilayer dewetting process.
Author: James Kela Yee Keen Grace
Publisher:
ISBN:
Category : Metallic films
Languages : en
Pages : 50
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This research was to verify the hypothesis that resistivity of metal's thin film deposited in a low-pressure environment is the same as its solid material. Thermal Evaporation is a thin film deposition technique in which metal inside a vacuum is evaporated, then deposited onto a surface. Higher quality metal films are deposited when the vacuum pressure is lower. At higher pressures, more air molecules are trapped within the layers of metal, thus increasing scattering sites and increasing the resistance. However, reaching a lower pressure requires more time and effort. In this research, films were deposited at various pressures and resistivities were calculated for each film to determine an ideal pressure range that creates the least resistivity.
Author: Adam Timothy Tate
Publisher:
ISBN:
Category :
Languages : en
Pages : 82
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