Effect of doping concentration on optical and electrical properties of intrinsic n-type ZnO (i-ZnO) and (Cu, Na and K) doped p-type ZnO thin films grown by chemical bath deposition method

Abstract

Pure ZnO and copper (IB group), sodium (IA group) and potassium (IA group) and doped ZnO thin films on glass substrate by chemical bath deposition method have been studied for Hall effect measurements, resistivity, Raman and photoluminescence (PL). The influence of dopant content on carrier concentration, electrical resistivity, and Hall mobility of the thin films are analyzed. Electrical conductivity measurements of ZnO are carried out by two probe method and activation energy for the electrical conductivity of pure and doped ZnO is found out. The Raman scattering of the pure ZnO and doped ZnO shows the first and second orders of polar and non-polar modes. Raman spectra confirms the hexagonal wurtzite structure of pure and doped ZnO with E 2 (high) mode at 439 cm −1 and presence of other possible defects. Photoluminescence (PL) at room temperature results indicate the emission occurs at close band lines and the outcomes are identified with a few inherent imperfections in the doped ZnO thin films. The PL results demonstrate the upgraded optoelectronic properties, specifically, the carriers for long life span is executed by the oxygen opportunities. Raman spectroscopy and photoluminescence confirm existence of zinc interstitials (Zni) as well as oxygen vacancies (Vo). Resistivity as low as 15 Ω-cm, Hall mobility as high as 6.2 cm 2 /Vs and effective carrier concentration as high as 1.70×10 17 e − /cm 3 have been obtained.

Design, Fabrication, and Packaging of an Optothermally Activated Nanocrystalline Pd–ZnO-Based Selective CO Sensor on a Screen-Printed In-Plane Heater

“…The amount of shallow donors formed first increases with an increase in doping concentration, which is due to the structural defects introduced in the lattice by the dopant atoms, and on further increasing the doping concentration beyond Pre_1, the defects and vacancies seem to decrease; this might be due to the electron scattering and Brustein Moss effect. 65,66 Similarly, oxygen vacancies are also present in Pre_2 and Pre_3 in the ratio 29 and 35%, respectively. By exploiting the PL and XPS data, the sample shows the maximum number of interstitial defects and vacancies for Pre_1.…”

Depth dependence of the photocatalytic reaction rate. kinetic model generalization

“…In such cases, the contribution of thermally excited charges must be considered as well. Detailed assessment of the number of charge carriers is based on experimental data published by other authors [19][20][21][22][23][24], and the corresponding approximations for calculations are presented in [16]. For these charges, the rate of contaminant degradation can be expressed by the following equation (equation ( 3)):…”

“…Its semiconductive properties are determined by donor levels, which can vary depending on the synthesis and posttreatment methods applied, ranging from 25 meV to 290 meV [19,53]. The number of current carriers can also vary significantly, particularly when dopants are used, ranging from 1.10 17 cm −3 [20][21][22]54] to 10 19 −10 20 cm −3 [21,23,54]. Therefore, the synthesis method of ZnO plays a crucial role in its properties and behavior under real conditions.…”

P-type Behaviour of Doped ZnO Thin Films Prepared by Chemical Bath Deposition

“…The carrier concentration of the samples as obtained from the Hall effect is of the order from 10 16 to ∼ 10 17 cm −3 [10] and we feel it is logical to employ a nondegenerate model to analyze the thermoelectric power data. Harry et al [11] have pointed out that A = (5/2) − r, where 'r' corresponds to the scattering index and is equal to -0.5 for piezoelectric scattering and -1.5 for ionized impurity scattering. Thus A = 3 for piezoelectric scattering and 4 for ionized impurity scattering.…”