br Deposition of MgSe thin films MgSe thin solid films

Deposition of MgSe thin films MgSe thin solid films were prepared using the versatile spray pyrolysis technique, which is simple and economic as compared to the MBE and MOCVD methods. The properties of the film can be controlled by adjusting the preparative parameters such as substrate temperature, spray rate, quantity of spray solution, pH of spray solution, etc. Aqueous solutions of magnesium chloride (MgCl2), selenium oxide (SeO2) and triethanolamine NH (CH2–CH2)3 (TEA) were prepared using double distilled water. The glass substrates were ultrasonically cleaned and purged with acetone prior to the deposition. The spray solution was prepared by mixing 10ml of 0.12M MgCl2, 10ml of 0.1M TEA and 10ml of 0.13M SeO2. The MgSe thin films of various thicknesses were deposited by spraying 5, 10, 15, 20, 25 and 30ml of spray solution onto preheated amorphous glass substrates, maintained at a temperature of 523K. The spray rate was kept at 4ml/min. The distance of 25cm was kept between the substrate and the nozzle. The MgSe film thickness was measured using weight difference method (by sensitive microbalance for thin films) and considering bulk density of MgSe. The X-ray diffractogram was recorded using PANalytical X\'Pert PRO MRD diffractometer with CuKα line in 2θ range from 20º to 90º. The compositional analysis of the deposited film was carried out by Energy Dispersive X-ray Spectroscopy and microstructure aspects of the films were studied with a JOEL\'S JSM-7600F Scanning Electron Microscope with the resolution of 1nm and an Atomic Force Microscope (AFM) from Park Scientific Instruments. The optical dopamine receptor antagonist spectrum was recorded using the JASCO V-530 UV/visible Spectrophotometer at normal incidence in the wavelength range from 300 to 900nm. The electrical resistivity of the film was measured in the temperature range from 300 to 550K by employing the two point probe method; quick drying silver paste was used as a contact material. A chromel–alumel thermocouple was used to measure the temperature of the sample. The type of electrical conductivity of the films was determined from the sign of the thermo-emf developed across the hot and cold junction.
Results and discussion
Conclusions Magnesium selenide thin films of thickness from 145 to 188nm were deposited onto glass substrates at 523K using the spray pyrolysis technique with varying the quantity of the spray solution. The grown films are nanocrystalline in nature with cubic structure. The crystallinity and the grain size of MgSe is improved with thickness. The films deposited by spraying 10ml of the solution are porous, showing growth of nano-rods. The optical band-gap energy decreases with an increase in film thickness. It is, therefore, concluded that the physical properties of the magnesium selenide films can be customized by merely controlling the film thickness, which in turn becomes suitable for a particular application.
Introduction White-light emitting diodes (W-LEDs) are one of the most promising eco-friendly light sources due to their low energy consumption [1]. W-LEDs offer benefits in terms of reliability, energy saving, and safety and therefore have drawn much attention in recent years [2,3]. To increase the efficiency of W-LEDs, special attention has recently been paid to the development of new phosphors with good luminescence properties that can be excited in the long-UV range (300–420nm). Blue phosphors are an important part in those new phosphors. Recently, W-LEDs have been used in many applications due to the developments in GaN-based chips and phosphor technology. The most popular products in the market are obtained by the combination of a blue-emitting phosphor (YAG:Ce3+), which suffer from the low color rendering index (CRI) and high color temperature (usually above 5500K). These drawbacks can be overcome by the use of triband W-LED, utilizing RGB (red, green and blue) tricolor phosphor coatings on the near ultraviolet (near-UV) LED chip. Blue phosphor BaMgAl10O17: Eu2+ (BAM:Eu2+) has been intensively studied [4,5]. However, BAM:Eu2+ has two major drawbacks: thermal degradation and UV damage, which lead to color shift and loss of brightness [6,7]. Apatite phosphors, which are naturally occurring materials, have recently been used for field-emission displays (FEDs) and would be suitable for white LEDs in the near future because of their low price, environmental friendliness, thermal stability and good photoluminescence properties [8]. Wang et al. [8] reported synthesis of a chloroapatite blue phosphor (Ca,Mg)5(PO4)3Cl:Eu with high quantum efficiency using a spray pyrolysis method. The color of the present W-LED depends completely on phosphors because the eyes are not sensitive to the UV output from the W-LED. The market share of the three-band W-LEDs based on near-UV chips has been steadily increasing. Eu2+ ions doped alkaline earth halophosphates are efficient blue-emitting phosphors used for triband W-LEDs. The hosts have been paid more attention in many studies because of their high quantum efficiencies and the excellent physical and chemical stabilities [9,10]. At the time they show very interesting physical, and, in particular, optical properties, [11,12]. Several solid solutions of alkaline earth halophosphates like Ca5(PO4)3Cl, Sr5(PO4)3Cl and Ba5(PO4)3Cl are known [13]. The substitution of Eu2+ for Ca2+ is facilitated by the similarity in ionic radii. These phosphors are normally synthesized by solid state reaction which requires very high temperature and it is time consuming also. This prompted us to go for alternative method for the synthesis of such phosphors which would be easy, needs low temperature and less time consuming than solid state reaction.