Abstract
Zinc selenide (ZnSe) thin films were deposited by RF magnetron sputtering in specific conditions, onto optical glass substrates, at different RF plasma power. The prepared ZnSe layers were afterwards subjected to a series of structural, morphological, optical and electrical characterizations. The obtained results pointed out the optimal sputtering conditions to obtain ZnSe films of excellent quality, especially in terms of better optical properties, lower superficial roughness, reduced micro-strain and a band gap value closer to the one reported for the ZnSe bulk semiconducting material. Electrical characterization were afterwards carried out by measuring the current–voltage (I-V) characteristics at room temperature, of prepared “sandwich”-like Au/ZnSe/Au structures. The analysis of I-V characteristics have shown that at low injection levels there is an Ohmic conduction, followed at high injection levels, after a well-defined transition voltage, by a Space Charge Limited Current (SCLC) in the presence of an exponential trap distribution in the band gap of the ZnSe thin films. The results obtained from all the characterization techniques presented, demonstrated thus the potential of ZnSe thin films sputtered under optimized RF plasma conditions, to be used as alternative environmentally-friendly Cd-free window layers within photovoltaic cells manufacturing.
Highlights
There is currently a high drive to develop semiconducting materials with easilytunable properties that allow improved light-matter interactions in order to expand the performance and functionality of various optoelectronic devices, such as: infrared-sensitive elements [1,2], light emitting diodes (LEDs) [3,4], or photovoltaic (PV) cells [5]
This paper presents the preparation of zinc selenide (ZnSe) thin films by radio frequency (RF) magnetron sputtering, since this deposition technique proved to ensure high quality chalcogen compounds-based films with excellent thickness uniformity, as demonstrated in our previous studies focused on the synthesis of
This behavior can be understood in terms of the low energy atoms which are adsorbed on the glass substrate, moving over and interacting to form clusters, but without posing enough energy to overcome the nucleation barrier, to reach thermodynamic stability that favors the formation of ZnSe crystallites
Summary
There is currently a high drive to develop semiconducting materials with easilytunable properties that allow improved light-matter interactions in order to expand the performance and functionality of various optoelectronic devices, such as: infrared-sensitive elements [1,2], light emitting diodes (LEDs) [3,4], or photovoltaic (PV) cells [5]. In this context, zinc selenide (ZnSe) is a very attractive material from AII -BVI binary semiconducting compounds with unique physical properties, such as, large direct band gap of 2.67 eV (at room temperature), low optical absorption in visible and infrared regions, high refractive index, high electrical conductivity, very good photosensitivity, and it is environmentally friendly [6]. This paper presents the preparation of ZnSe thin films by radio frequency (RF) magnetron sputtering, since this deposition technique proved to ensure high quality chalcogen compounds-based films with excellent thickness uniformity, as demonstrated in our previous studies focused on the synthesis of
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