Titanium-doped sapphire is a phonon-terminated laser crystal which is applied in many fields. But residual infrared absorption in laser operation region of the crystal hindered the improvement of the crystal quality.T...Titanium-doped sapphire is a phonon-terminated laser crystal which is applied in many fields. But residual infrared absorption in laser operation region of the crystal hindered the improvement of the crystal quality.The macroscopic defects in the crystal often perplexed growers.展开更多
Calculating the impact of point defects on the macroscopic properties of technologically relevantsemiconductors remains a considerable challenge. Semi-empirical approaches, such as the tightbindingmethod, are very eff...Calculating the impact of point defects on the macroscopic properties of technologically relevantsemiconductors remains a considerable challenge. Semi-empirical approaches, such as the tightbindingmethod, are very efficient in calculating the electronic structure of large supercells containingone or several defects. However, the accuracy of these calculations depends on the quality of theparameters. Obtaining reliable parameters by fitting to the large number of entangled bands indefective supercells is a demanding task.We therefore present an alternative way by fitting to the atomand orbital projected densities of states. Starting with a tight-binding fit of the pristine material,we onlyneed a few physically motivated parameters for the fitting of defects. The training is done on data setsgenerated purely with parameter variations of tight-binding Hamiltonians. We demonstrate theefficiency of our approach for the calculation of the carbon monomer and the carbon dimersubstitutions in hexagonal boron nitride. The method opens a path towards understandingcomplicated defect landscapes using a computationally affordable semi-empirical approach withoutsacrificing accuracy.展开更多
文摘Titanium-doped sapphire is a phonon-terminated laser crystal which is applied in many fields. But residual infrared absorption in laser operation region of the crystal hindered the improvement of the crystal quality.The macroscopic defects in the crystal often perplexed growers.
基金funded by the Luxembourg National Research Fund(FNR),grant reference PRIDE17/12246511/PACEin part by the Austrian Science Fund(FWF)10.55776/COE5.We would like to acknowledge Christoph Schattauer and Mohamed Ali Abdulmalik for fruitful discussions.
文摘Calculating the impact of point defects on the macroscopic properties of technologically relevantsemiconductors remains a considerable challenge. Semi-empirical approaches, such as the tightbindingmethod, are very efficient in calculating the electronic structure of large supercells containingone or several defects. However, the accuracy of these calculations depends on the quality of theparameters. Obtaining reliable parameters by fitting to the large number of entangled bands indefective supercells is a demanding task.We therefore present an alternative way by fitting to the atomand orbital projected densities of states. Starting with a tight-binding fit of the pristine material,we onlyneed a few physically motivated parameters for the fitting of defects. The training is done on data setsgenerated purely with parameter variations of tight-binding Hamiltonians. We demonstrate theefficiency of our approach for the calculation of the carbon monomer and the carbon dimersubstitutions in hexagonal boron nitride. The method opens a path towards understandingcomplicated defect landscapes using a computationally affordable semi-empirical approach withoutsacrificing accuracy.
