Effects of annealing on the properties and structure of electrodeposited semiconducting Cu–O thin films

Abstract

The structures and the electronic states in electrodeposited semiconductor Cu -O thin films have been investigated for each annealing temperature (T A ) by X-ray diffraction (XD) and X-ray absorption spectroscopy (XAS) near the Cu K edge using synchrotron radiation. The thin films prepared as grown and annealed at T A ≤ 175 °C, 200 °C ≤ T A ≤ 300 °C, T A = 400 °C are characterized mainly by the pure Cu 2 O-type structure, the pseudo-Cu 2 O-type having a superlattice structure, and two phases of Cu 2 O-type and CuOtype structures, respectively, while the film annealed at T A = 500 °C is single-phase CuO-type. The XAS spectra suggest that there is a structural phase transition occurring at about 400 °C, which induces a modulation of the local structure around Cu ions observed in the extended X-ray absorption fine structure (EXAFS) and the occupational electronic band states of Cu-4p localized just above the Fermi level, taken from X-ray absorption near edge structure (XANES). The open-circuit voltage suggests that the photosensitivity of the Cu -O thin films strongly depends on the annealing treatment and shows a crossover from an n-type to a p-type semiconductor.

Formation of CuO nanorods and their bundles by an electrochemical dissolution and deposition process

“…The two electrodes were immersed in 100 ml of deionized water and a voltage of 10-30 V DC was applied [19,20]. The electrochemical dissolution and deposition were performed by varying the electrode separations from 2 to 10 mm and the deposition time from 1 to 8 h. The as-deposited samples were dried for 1 h and annealed at 300-500 • C for 30 min in an atmosphere of air [14]. Morphology of the films was characterized by scanning electron microscopy (SEM, JEOL JSM-6335F).…”

“…CuO NSs are regarded as promising materials for many potential applications such as electrodes in dye-sensitized solar cells [2,3], capacitors [4], gas sensors, field effect transistors [5], anode materials for lithium-ion batteries [6], antimicrobials [7], humidity sensors [8] and diodes [9]. A number of synthesis methods for CuO NSs have been detailed in the literature, for example thermal plasma [6], hydrothermal [10], sparking [11,12], electroplating of copper (Cu) thin films with thermal annealing [13], electrochemical [14], sol-gel [15], thermal evaporation [16] and pulsed laser deposition [17]. Electrochemical methods for the formation of CuO NSs are of particular interest due to the many advantages over other methods including its low cost, ease of process and the various available types of electrolyte [18].…”

Electrodeposited Cu2O Thin Films for Fabrication of CuO/Cu2O Heterojunction

“…These results convince that the thin films are high quality single phase Cu 2 O and CuO structures (free of amorphous phases and impurities). Detail investigation has been reported (Wijesundera et al, 2007). It is characterised that single phase Cu 2 O thin films are converted to two phase Cu 2 O and CuO composit films with increasing the annealing temperature.…”

Structural regulation of electrochemically deposited copper layers for fabrication of thin film solar cells with a CuInS2 photoabsorber

“…However, due to the specific electrochemical irreversibility of sulfur different from selenium, there have been only a few reports on fabrication of one-step electrodeposited CuInS 2 films. For the electrodeposition of CuInS 2 , therefore, a sequential route consisting of electrodeposition of Cu and In staked layers followed by sulfurization under H 2 S gas or sulfur vapor has been studied [8,9]. In this route, physicochemical properties of both Cu and In layers, e.g., compactness, thickness variations (uniformity), and surface roughness, have significant effects on the formation of a well-controlled absorber for an efficient solar cell.…”