Nickel oxide (NiO) films have potential applications in optical coatings, ultraviolet detectors, gas sensors and perovskite solar cells. The great improvement in electrical conduction is still critical for NiO films so far. NiO films are usually p-type conductive because of the native Ni vacancies and interstitials O. These native point defects make n-type NiO difficult to prepare. Even that, n-type NiO films with improved electrical conduction still need to be prepared for n-NiO-based heterojunction devices. Herein the face-centered cubic NiO:Zn2+ films are magnetron reactively sputtered on the glass substrates at different substrate temperatures (Tsub). The introduction of Zn2+ to NiO leads to the transition in conduction from p to n at 400 °C Tsub. The films are almost improved in crystallization with increase in Tsub, thereby reducing the point defect content i.e. the free carrier concentration. The resulting films are also improved in optical transmittance with increase in Tsub. The film’s optical energy gap is tunable in the range of 3.6 eV through 3.8 eV with Tsub.

Nickel oxide (NiO) films are direct current sputtered at different substrate temperatures (Tsub) using high sputtering power density and sputtering pressure. The improvement in crystallization of the films with Tsub results in the decrease of concentration of the coexisting Ni vacancies and interstitial O atoms, thereby increasing the hole mobility and resistivity. All the films have an approximate near-violet absorption edge of ca. 3.6 eV. The only difference is the rate of increase of transmittance that is attributed to the tail states produced by the tensile stress. The polycrystalline NiO film with 200 oC Tsub can be used as the hole-transporting layer material of inverse-architecture perovskite solar cells due to the maximum free hole concentration, minimum resistivity and intermediate hole mobility.

Highly crystallized silver oxide (Ag x O) films have been room-temperature deposited on glass substrates by direct-current (dc) magnetron sputtering with high sputtering power density. The impact of flow rate ratio of O 2 to Ar gases (O 2 /Ar) is in particular studied on the microstructure pattern, optical and electrical behaviors of the Ag x O films especially pure AgO films. An evolution in phase clearly occurs with increase of O 2 /Ar. The absorption edge in unit eV of the Ag x O film composed of AgO and Ag 2 O, and the pure AgO films slightly varies near 2.7 eV with O 2 /Ar. The pure AgO films are best crystallized at 2:1 O 2 /Ar, and overdose of O worsens the crystallization of the AgO films, due to the lattice distortion mainly arising from Ag vacancies and interstitial O. The free carrier concentration and resistivity of fully oxidized Ag x O film and AgO films are reduced and then increased with increase of O 2 /Ar. Cubic phases Ag 2 O and AgO are both p-type conductive, mainly due to the O vacancies, and Ag vacancies and interstitial O, respectively. The pure AgO films have high carrier mobility that is strongly affected by the point defects including vacancies and interstitial atoms.RECEIVED

A series of non-stoichiometric p-type silver oxide (AgxO) films are room temperature deposited on glass substrates at different deposition time (td) by dc magnetron sputtering with high sputtering power. The evolution in component and the change in electrical and optical properties of the films with td are studied by XRD, SEM, EDS, visible-infrared spectroscopy and Hall data. The p-type conduction of cubic AgO and Ag2O phases is also proposed in mechanism. The evolution in component from AgO to almost Ag2O and the change in microstructure with td are caused by the thermal decomposition of AgO phase induced by high sputtering power. The film’s absorption edge firstly redshifts from 2.8 to 2.3 eV with increase of td from 2 min to 15 min, and then is suddenly reduced to 1.25 eV of cubic phase Ag2O at 20 min td. The phases AgO and Ag2O both have p-type conduction characteristics, mainly due to the Ag vacancies and O vacancies, respectively. The free carrier concentration and the resistivity of the films are both increased and reduced with increase of td. The AgxO film with 15 min td is the highest in p-type conduction ability due to the highest free carrier concentration and mobility, and thus is capable of being the candidate of hole-transporting layer materials of perovskite solar cells.

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