Abstract In the past 10 years, ZnO as a semiconductor has attracted considerable attention due to its unique properties, such as high electron mobility, wide and direct band gap and large exciton binding energy. ZnO has been considered a promising material for optoelectronic device applications, and the fabrications of high quality p-type ZnO and p–n junction are the key steps to realize these applications. However, the reliable p-type doping of the material remains a major challenge because of the self-compensation from native donor defects (V O and Zn i ) and/or hydrogen incorporation. Considerable efforts have been made to obtain p-type ZnO by doping different elements with various techniques. Remarkable progresses have been achieved, both theoretically and experimentally. In this paper, we discuss p-type ZnO materials: theory, growth, properties and devices, comprehensively. We first discuss the native defects in ZnO. Among the native defects in ZnO, V Zn and O i act as acceptors. We then present the theory of p-type doping in ZnO, and summarize the growth techniques for p-type ZnO and the properties of p-type ZnO materials. Theoretically, the principles of selection of p-type dopant, codoping method and X Zn –2V Zn acceptor model are introduced. Experimentally, besides the intrinsic p-type ZnO grown at O-rich ambient, p-type ZnO (MgZnO) materials have been prepared by various techniques using Group-I, IV and V elements. We pay a special attention to the band gap of p-type ZnO by band-gap engineering and room temperature ferromagnetism observed in p-type ZnO. Finally, we summarize the devices based on p-type ZnO materials.

RaoP-Type ZnO Materials: Theory, Growth, Properties, and Devices

Thin film photocatalysis for environmental remediation: A status review

A comprehensive study of opto-electrical and nonlinear properties of Cu@CdS thin films for optoelectronics

The facile and cost-effective fabrication of cadmium sulphide (CdS) thin films with diverse contents of Zn was carried out on substrates of glass which maintained at 300 °C temperature. The grown CdS films are observed to belong monophasic hexagonal system at all Zn contents through structural and vibrational inspections. The values of crystallites size were determined in range of 16–31 nm. The Zn existence and its homogeneity were confirmed by EDX and e-mapping. SEM study displayed the modification in surface topography of CdS films by Zn content. Ultra violet-visible-near infrared spectroscopy study revealed that the grown films are of good optical transparency. The indices of refraction values were estimated and shows the variation in range of 1–2.8 owing to Zn. The PL study propose the applications of grown films in green LEDs as the emission peak has been observed at 513 ± 17 nm. Third-order-nonlinear optics (TONLO) constraints were determined through off and on orifice Z-scan data. The order of the values of TONLO index of refraction and susceptibility was noted of 10−8 cm2/W and 10−5 esu, orders correspondingly and found to be enhanced with Zn doping in CdS. Enhancement in optical limiting behaviour of CdS was also noticed when doped with Zn.

An effect of Zn content doping on opto-third order nonlinear characteristics of nanostructured CdS thin films fabricated through spray pyrolysis for optoelectronics

The influences of transition metals (Sc, Ti, V, Cr and Mn) doping at different distances on the stability, electronic structure, conductivity and optical properties of CdS are studied by using VASP code. The results show that the Cr-doped CdS is easy to form, followed by V, Ti, Sc and Mn. The next nearest-neighbor doping is the most stable in each transition metal-doped system. The band-gaps gradually decrease with the order of Sc, Ti, V, Cr, Mn-doping, all doped systems become the degenerate semiconductor. Doping not only enhances conductivity, but also improves photocatalytic performance, especially Mn-doped CdS has obvious improvement. The absorption intensity in the visible light range of the single-doping is more than that of two atoms doped system in different distances, of which Mn and Cr single-doping are the most prominent.

Effect of transition metals (Sc, Ti, V, Cr and Mn) doping on electronic structure and optical properties of CdS

Activated carbon from cashew nut shell via a potassium hydroxide (KOH) at 600 °C in an N2 atmosphere and their characteristics using FT-IR, XRD, SEM with EDS, and BET analysis was investigated. The cashew nut shell activated carbon obtained by KOH activation with a CNS/KOH ratio of 1:1 at 600 °C (N2 atmosphere) for 2 h had the highest surface area (407.80 m2/g) as compared to other ratio samples. Amongst, CNS/KOH ratios of 1:1 sample are used for the adsorbent, they are effects of contact time, pH, adsorbent dose, and initial dye concentration on brilliant green (BG) removal efficiency were studied. Moreover, the Langmuir and Freundlich adsorption models consisted utilized to affirm the adsorption isotherms. They are, best fitting for BG experimental equilibrium data was achieved with the Langmuir isotherm, giving a maximum BG adsorption capacity of 243.90 mg/g. 

Adsorption of brilliant green dye onto activated carbon prepared from cashew nut shell by KOH activation: Studies on equilibrium isotherm.

Spray technique using perfume atomiser is used to deposit Ba-doped CdS (CdS:Ba) thin films on glass substrates. Barium concentration is varied as 0, 1, 2 and 3 wt-% and the effect of Ba doping level on some physical properties of the CdS films is reported in this paper. XRD studies confirm that the undoped and doped films exhibit hexagonal crystal structure with a strong (0 0 2) preferential orientation. Nanosized rod shaped grains are evinced for the heavily doped films. The mapping images confirm the distribution of the host ions Cd, S and the dopant ion Ba on the film surface. Increased transparency is observed for the doped films. Magnetic studies confirm that the doped films exhibit ferromagnetic behaviour. The obtained results confirm that barium, a cationic dopant ion enhances the optical and magnetic properties of CdS thin films to a large extent.

Optical and magnetic properties of Ba-doped CdS thin films

Improved magnetic and photocatalytic properties of spray deposited (Li+Co) codoped CdS thin films

Li-doped CdS (CdS:Li) thin films with 0, 1, 2 and 3 wt-% Li concentrations were prepared by the spray technique using a perfume atomiser. The effect of Li doping concentration on the structural, op...

P. Samiyammal

Papers

Adsorption of brilliant green dye onto activated carbon prepared from cashew nut shell by KOH activation: Studies on equilibrium isotherm.

Optical and magnetic properties of Ba-doped CdS thin films

Improved magnetic and photocatalytic properties of spray deposited (Li+Co) codoped CdS thin films

Doping effect investigation of Li-doped CdS thin films

(Ba+Co) codoped CdS thin films with enhanced magnetic and photodegradation properties