The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Aron Walsh - One of the best experts on this subject based on the ideXlab platform.
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defect physics of the kesterite thin film solar cell absorber cu2znsns4
Applied Physics Letters, 2010Co-Authors: Shiyou Chen, X G Gong, Aron WalshAbstract:Cu2ZnSnS4 is one of the most promising quaternary absorber materials for thin-film solar cells. Examination of the thermodynamic stability of this quaternary Compound reveals that the stable chemical potential region for the formation of Stoichiometric Compound is small. Under these conditions, the dominant defect will be p-type CuZn antisite, which has an acceptor level deeper than the Cu vacancy. The dominant self-compensated defect pair in this quaternary Compound is [CuZn−+ZnCu+]0, which leads to the formation of various polytype structures of Cu2ZnSnS4. We propose that to maximize the solar cell performance, growth of Cu2ZnSnS4 under Cu-poor/Zn-rich conditions will be optimal, if the precipitation of ZnS can be avoided by kinetic barriers.
Greczynski Grzegorz - One of the best experts on this subject based on the ideXlab platform.
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Self-organized columnar Zr0.7Ta0.3B1.5 core/shell-nanostructure thin films
'Elsevier BV', 2020Co-Authors: Bakhit Babak, Palisaitis Justinas, Persson, Per O.Å., Alling Björn, Rosen Johanna, Hultman Lars, Petrov Ivan, Greene, Joseph E, Greczynski GrzegorzAbstract:We recently showed that Zr1−xTaxBy thin films have columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. Layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we determine the atomic-scale nanostructure of sputter-deposited columnar Zr0.7Ta0.3B1.5 thin films. The columns, 95 ± 17 Å, are core/shell nanostructures in which 80 ± 15-Å cores are crystalline hexagonal-AlB2-structure Zr-rich Stoichiometric Zr1−xTaxB2. The shell structure is a narrow dense, disordered region that is Ta-rich and highly B-deficient. The cores are formed under intense ion mixing via preferential Ta segregation, due to the lower formation enthalpy of TaB2 than ZrB2, in response to the chemical driving force to form a Stoichiometric Compound. The films with unique combination of nanosized crystalline cores and dense metallic-glass-like shells provide excellent mechanical properties
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Self-organized columnar Zr0.7Ta0.3B1.5 core/shell-nanostructure thin films
'Elsevier BV', 2020Co-Authors: Bakhit Babak, Palisaitis Justinas, Persson, Per O.Å., Alling Björn, Rosen Johanna, Hultman Lars, Petrov Ivan, Greene, Joseph E, Greczynski GrzegorzAbstract:We recently showed that Zr1−xTaxBy thin films have columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. Layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we determine the atomic-scale nanostructure of sputter-deposited columnar Zr0.7Ta0.3B1.5 thin films. The columns, 95 ± 17 Å, are core/shell nanostructures in which 80 ± 15-Å cores are crystalline hexagonal-AlB2-structure Zr-rich Stoichiometric Zr1−xTaxB2. The shell structure is a narrow dense, disordered region that is Ta-rich and highly B-deficient. The cores are formed under intense ion mixing via preferential Ta segregation, due to the lower formation enthalpy of TaB2 than ZrB2, in response to the chemical driving force to form a Stoichiometric Compound. The films with unique combination of nanosized crystalline cores and dense metallic-glass-like shells provide excellent mechanical properties.Funding agencies: Knut and Alice Wallenberg (KAW) FoundationKnut & Alice Wallenberg Foundation [KAW 2015.0043]; electron microscopy laboratory in Linkoping; Swedish Research Council VRSwedish Research Council [2014-5790, 2018-03957, 2019-05403, 642-2013-8020]; VINNOVA Gran
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A simple model for non-saturated reactive sputtering processes
'Elsevier BV', 2019Co-Authors: Nyberg T., Greczynski Grzegorz, Högberg Hans, Berg S.Abstract:Reactive sputtering processes are quite complex processes and therefore difficult to understand in detail. However, a number of attempts to clearify the behaviour of reactive sputtering of oxides and nitrides have been made. Several process modelling results for such processes have been published that reasonable well mirrors the actual experimental findings. All of these models indicate that the processes normally exhibit hysteresis effects and that the oxides/nitrides will saturate at the Stoichiometric Compound values. We therefore call these processes saturated reactive sputtering processes. Carrying out reactive sputtering in a hydrocarbon gas like CH4 instead of in oxygen or nitrogen cannot be described with the previously suggested models for oxide or nitride formations. Decomposition of the CH4 molecule in the plasma may result both in carbide formation with the target metal as well as plasma deposited carbon. Depending on the supply of the CH4 the deposited film composition may vary from 0 to 100% of carbon. In the extreme case of very high supply of CH4 a pure carbon film will be deposited. We expect that similar behaviour will be found when carrying out reactive sputtering in other solid material containing gases like e.g. silane or diborane. We have chosen to call such processes non-saturated reactive sputtering processes. In order to understand the behaviour of non-saturated reactive sputtering processes we have developed a new model that enables the user to find the response to individual processing parameters and thus obtain a tool for process optimization. In order to limit the number of parameters our model is outlined for reactive sputtering of Ti in a mixture of argon and CH4. In this article we report that the simulation results reasonable well correlate with our experimental findings.Funding Agencies|Carl Tryggers Foundation [CTS 17:336, CTS 15:219, CTS 14:431]; Swedish Government Strategic Research Area in Materials Science on Advanced Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [KAW2016.0358]; Swedish Research Council VR Grant [2018-03957]; VINNOVA GrantVinnova [2018-04290]; Carl Tryggers Stiftelse [CTS 17:166]
H L Hwang - One of the best experts on this subject based on the ideXlab platform.
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development of a comprehensive design tool for non Stoichiometric Compound thin film solar cells calculations of the opto electrical properties of multinary alloy and optimization of the cell performance
Journal of Physics and Chemistry of Solids, 2005Co-Authors: H L Hwang, H H ChangAbstract:Abstract Based on our previously developed design methodologies which minimized the total free energy and the calculations of the defect/carrier concentrations and the carrier mobility of the non-Stoichiometric CuInSe2, CuGaSe2, ZnO and ZnO:Al, good confirmation was obtained from our computed conductance of CuInSe2 with the measured data, in which the total energy calculation was modified by considering the configurational entropy, and solving the coupled total free energy function and the charge neutrality equation self-consistently. In addition, a method to calculate the opto-electrical properties of CuInxGa1−xSe2 alloy, which is the most popular absorber for high efficiency thin film solar cells, was also effectively developed. Furthermore, the above electrical parameters of the non-Stoichiometric window/absorber layers were used to optimize the cell structure, and their performances were correlated with the published experimental results.
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development of an intelligent design tool for non Stoichiometric Compound devices an example
Materials Science in Semiconductor Processing, 2003Co-Authors: H H Chang, Herngyih Ueng, H L HwangAbstract:Abstract In this paper, we discuss the idea of intelligent design of thin film CIGS solar cell, and we focus on the methodology of material design. We first introduce the calculation of the neutral defect concentrations of non-Stoichiometric CuInSe 2 , CuGaSe 2 and ZnO under specific atomic chemical potential conditions, and predict the formation of the order defect Compound using the concept of minimization of total free energy, which includes the configurational entropy. This calculation is the main procedure in the material design and the key to the device design and process design. We then calculate the carrier concentrations using multi-level defect statistics and mobilities of these materials of different constitutions. The functions of the intelligent design tool are demonstrated.
Shiyou Chen - One of the best experts on this subject based on the ideXlab platform.
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defect physics of the kesterite thin film solar cell absorber cu2znsns4
Applied Physics Letters, 2010Co-Authors: Shiyou Chen, X G Gong, Aron WalshAbstract:Cu2ZnSnS4 is one of the most promising quaternary absorber materials for thin-film solar cells. Examination of the thermodynamic stability of this quaternary Compound reveals that the stable chemical potential region for the formation of Stoichiometric Compound is small. Under these conditions, the dominant defect will be p-type CuZn antisite, which has an acceptor level deeper than the Cu vacancy. The dominant self-compensated defect pair in this quaternary Compound is [CuZn−+ZnCu+]0, which leads to the formation of various polytype structures of Cu2ZnSnS4. We propose that to maximize the solar cell performance, growth of Cu2ZnSnS4 under Cu-poor/Zn-rich conditions will be optimal, if the precipitation of ZnS can be avoided by kinetic barriers.
H H Chang - One of the best experts on this subject based on the ideXlab platform.
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development of a comprehensive design tool for non Stoichiometric Compound thin film solar cells calculations of the opto electrical properties of multinary alloy and optimization of the cell performance
Journal of Physics and Chemistry of Solids, 2005Co-Authors: H L Hwang, H H ChangAbstract:Abstract Based on our previously developed design methodologies which minimized the total free energy and the calculations of the defect/carrier concentrations and the carrier mobility of the non-Stoichiometric CuInSe2, CuGaSe2, ZnO and ZnO:Al, good confirmation was obtained from our computed conductance of CuInSe2 with the measured data, in which the total energy calculation was modified by considering the configurational entropy, and solving the coupled total free energy function and the charge neutrality equation self-consistently. In addition, a method to calculate the opto-electrical properties of CuInxGa1−xSe2 alloy, which is the most popular absorber for high efficiency thin film solar cells, was also effectively developed. Furthermore, the above electrical parameters of the non-Stoichiometric window/absorber layers were used to optimize the cell structure, and their performances were correlated with the published experimental results.
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development of an intelligent design tool for non Stoichiometric Compound devices an example
Materials Science in Semiconductor Processing, 2003Co-Authors: H H Chang, Herngyih Ueng, H L HwangAbstract:Abstract In this paper, we discuss the idea of intelligent design of thin film CIGS solar cell, and we focus on the methodology of material design. We first introduce the calculation of the neutral defect concentrations of non-Stoichiometric CuInSe 2 , CuGaSe 2 and ZnO under specific atomic chemical potential conditions, and predict the formation of the order defect Compound using the concept of minimization of total free energy, which includes the configurational entropy. This calculation is the main procedure in the material design and the key to the device design and process design. We then calculate the carrier concentrations using multi-level defect statistics and mobilities of these materials of different constitutions. The functions of the intelligent design tool are demonstrated.