Fe-doped ZnS films of high optical quality were fabricated using vacuum vapor deposition. Preferential crystalline orientation and phase purity of the host ZnS films were increased by the addition of small amounts of Fe, and the spectral shape of the 2-4 µm absorption peak is maintained up to the highest concentration tested (9 at.% ). However, Raman shifts of the Fe:ZnS films indicate the inclusion of disordered material at high Fe concentrations, and below-gap optical Kerr effect measurements show an increase in χ (3) correlated with this data. Nonlinear optical properties of the films were also measured using the Z-scan method at 532 nm, and saturable absorption of the Fe-based intraband levels at 2.94 µm was confirmed. Spectroscopy and laser demonstration of a new class of gain media," IEEE J. Quantum Electron. 32, 885-895 (1996) The scherrer formula for x-ray particle size determination," Phys. Rev. 56, 978-982 (1939).
No abstract
Thin films of Cr and Fe-doped ZnS suitable for waveguide mid-IR applications, with well-isolated TM 2+ peaks, and Cr 2+ absorption and fluorescence comparable to bulk crystals were investigated. Raman data indicate that the TM is substitutional.
We report the results of the extensive spectral-luminescent characterization including concentration quenching analysis of the first laser-quality vapor-deposited Cr:ZnS films, and demonstrate their use as saturable absorbers. Comparison of spectral-luminescent properties with bulk Cr:ZnS indicates their high laser quality, opening the way towards industrial mid-IR thin-disk and waveguide lasers. Successful implementation of the grown films in a Q-switched Er,Yb:GdAB solid-state laser emitting at 1.52 μm gives clear experimental evidence of the high quality of the films.
Copper oxide (Cu 2 O) is an abundant non-toxic intrinsic p-type semiconductor [1], with a long exciton lifetime [2], low-cost producibility, and a direct band gap of 2.1 eV. It has therefore attracted much attention in the photovoltaic solar cell community [1]. However, the discrepancy between the theoretical efficiency (approaching 12% [3]) and the efficiency actually achieved with technologies available (<2% [4,5]) resulted in a lack of further interest in Cu 2 O as a possible photovoltaic material. Besides the low efficiency obtained, another major drawback of Cu 2 O was the difficulty in controlling the electrical properties due to its intrinsic p-type conductivity as a result of copper vacancies [6]. More recently, there has been a resurgence of interest in Cu 2 O as a photovoltaic. In 2016, the highest Cu 2 O solar cell efficiency achieved had increased (to 8.1% [7]), but is still poor compared to competing materials.Luque et al proposed a concept of intermediate band solar cells (IBSCs) which can solve the problem of low efficiency: with the creation of a partially filled band within the band gap, the electrons not only jump from the valence band (VB) into the conduction band (CB) by absorption of at least the energy of the band gap (E g ) as in single gap solar cells, but also lower photon energies are absorbed, allowing the transition of carriers from the VB into the CB by using the IB as a 'stepping stone'. Therefore, the Shockley-Queisser limit [8] is overcome, making theoretical conversion efficiencies of such solar cells up to 20% higher than single gap solar cells [9]. Several major strategies exist for creating IBSCs: including multiple quantum dots layers [10], doping with highly mismatched elements [11] or doping with a suitable element which forms delocalized energy levels in the band gap [12,13] are all suggested as viable methods.The need to control the electrical properties of Cu 2 O translates into the need to select suitable elements with which dope the host material. Due to concerns of damaging or distressing the bulk host, and because it is not a standard industry method, ion implantation of high dopant densities is one of the least investigated methods of creating an IBSC [14]. Nevertheless, attempts to implant Cd, In and Cl in Cu 2 O have been made, and have shown promise [15][16][17]. Nitrogen also appeared as a promising dopant option, not only for being nontoxic, low-cost and easily accessible, but also because it has a similar atomic radius to oxygen, and hence may be possible to substitute,
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