Effect of growth parameters on the properties of RF-sputtered highly conductive and transparent p-type NiO_xfilms

Abstract

Highly conductive and transparent NiO x films can be very useful as buffer layers for the optimization of the p-type contacts of optoelectronic devices. Thin NiO x films were fabricated by reactive radio frequency (RF) sputtering at room temperature starting from a Ni target. A systematic study of the influence of oxygen partial pressure, RF power and sputtering gas pressure on the films' properties was carried out. The structural, microstructural, optical and electrical properties were affected differently by the sputtering parameters. Resistivity decreased by increasing the oxygen partial pressure and the sputtering total pressure and by decreasing the RF power, while transmittance increased by decreasing the oxygen partial pressure and by increasing the RF power and sputtering pressure. Minimum resistivity of 1.6×10 −2 Ωcm and a visible transmittance of 40% were achieved for a film grown in a pure oxygen atmosphere, while a higher transmittance of 54% and a resistivity of ρ=1.1×10 −1 Ωcm were obtained for a film grown at 30% oxygen partial pressure. The trends of transmittance and resistivity as a function of the oxygen pressure during the sputtering process can be explained in terms of the amount of Ni 3+ defects deduced by x-ray photoelectron spectroscopy (XPS) measurements. The full interpretation of the other results is less straightforward and highlights the relevance of the samples' structural properties.

Effect of NiOx’s film thickness on the electrical properties of Ni/p–NiOx/n-Si structures

“…Additionally, the electrical conductivity of NiO depends on the presence of nickel cation vacancy or interstitial oxygen. Simplified reaction to explain formation of one nickel vacancies is given in equation (1) [9] and also supported by Figure 1 adapted in Cho et al.’s [10] study …”

“…As a result of the short literature review, it can be said that there are lot of techniques that have been used to grow NiO x films including sol-gel [15], pulsed laser deposition [16], spray pyrolysis [17] and radio frequency (RF) magnetron sputtering [18]. Among these, the RF sputtering technique has been widely used to obtain nonstoichiometric NiO x films due to its industrial scalability, that is, the properties of the films have been controlled by changing sputtering conditions like substrate temperature, O 2 flow rate and RF power [9,19]. With respect to our previously published paper [20] and to the studies reported in the literature [21][22][23], in this work, we investigated the effect of the thickness of NiO x films on the electrical properties of Ni/p-NiO x /n-Si devices.…”

Engineered optical and electrical performance of rf–sputtered undoped nickel oxide thin films for inverted perovskite solar cells

“…3 . The existence of Ni 3+ suggests the existence of V Ni because two Ni 2+ ions react with oxygen and produce two Ni 3+ ions and vacancy, following the reaction below 32 – 34 , The binding energy of Ni 2+ and Ni 3+ for the Ni 2p 3/2 peaks are located around 853.7 and 855.8 eV, respectively. An additional peak located at around 863 eV is the satellite of Ni 2p 3/2 .…”

Evaluating Materials Design Parameters of Hole-Selective Contacts for Silicon Heterojunction Solar Cells

“…Namely, we expect E VB,NiO x to shift toward vacuum with increased x and the band gap E G to decrease, as elaborated subsequently. Additionally, it has been reported by numerous studies that increasing O 2 flow during sputter growth reduces resistivity (i.e., increases conductivity) in p-type NiO x [43], [50]- [53]. Some reports indicate an increase in hole doping and decrease in mobility [52], [53], but trends and magnitudes are inconsistent [43], [51].…”