We have developed a low-temperature atomic layer deposition (ALD) process for depositing crystalline and phase pure spinel cobalt oxide (Co3O4) films at 120 °C using [Co(tBu2 DAD)2] and ozone as co-reagent. X-ray diffraction, UV-Vis spectroscopy, atomic force microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy and time-of-flight elastic recoil detection analysis were performed to characterize the structure and properties of the films. The as-deposited Co3O4 films are crystalline with low amount of impurities (<2 % C and <5 % H) despite low deposition temperatures. Deposition of Co3O4 onto thin TiO2 photoanodes (100 nm) for water oxidation resulted in 30 % improvement of photocurrent (after 10 ALD cycles yielding small Co3O4 particles) as compared to pristine TiO2 films), and exhibited no detrimental effects on photocurrent response up to 300 deposition cycles (approximately 35 nm thick films), demonstrating the applicability of the developed ALD process for deposition of effective catalyst particles and layers in photoelectrochemical water-splitting devices.
High-performance p-type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low 1 hole mobility and high off-state currents. We fabricated p-type TFTs with a phasepure polycrystalline Cu 2 O semiconductor channel grown by atomic layer deposition (ALD). The TFT switching characteristics were improved by applying a thin ALD Al 2 O 3 passivation layer on the Cu 2 O channel, followed by vacuum annealing at 300 • C. Detailed characterisation by TEM-EDX and XPS shows that the surface of Cu 2 O is reduced following Al 2 O 3 deposition and indicates the formation of 1-2 nm thick CuAlO 2 interfacial layer. This, together with field-effect passivation caused by the high negative fixed charge of the ALD Al 2 O 3 , leads to an improvement in the TFT performance by reducing the density of deep trap states as well as by reducing the accumulation of electrons in the semiconducting layer in the device off-state.
Herein, we report an atomic layer
deposition (ALD) process for
Cu
2
O thin films using copper(II) acetate [Cu(OAc)
2
] and water vapor as precursors. This precursor combination enables
the deposition of phase-pure, polycrystalline, and impurity-free Cu
2
O thin films at temperatures of 180–220 °C. The
deposition of Cu(I) oxide films from a Cu(II) precursor without the
use of a reducing agent is explained by the thermally induced reduction
of Cu(OAc)
2
to the volatile copper(I) acetate, CuOAc. In
addition to the optimization of ALD process parameters and characterization
of film properties, we studied the Cu
2
O films in the fabrication
of photoconductor devices. Our proof-of-concept devices show that
approximately 20 nm thick Cu
2
O films can be used for photodetection
in the visible wavelength range and that the thin film photoconductors
exhibit improved device characteristics in comparison to bulk Cu
2
O crystals.
Copper(II) oxide thin films were grown by atomic layer deposition (ALD) using bis-(dimethylamino-2-propoxide)copper [Cu(dmap)2] and ozone in a temperature window of 80–140 °C. A thorough characterization of the films was performed using x-ray diffraction, x-ray reflectivity, UV-Vis spectrophotometry, atomic force microscopy, field emission scanning electron microscopy, x-ray photoelectron spectroscopy, and time-of-flight elastic recoil detection analysis techniques. The process was found to produce polycrystalline copper(II) oxide films with a growth rate of 0.2–0.3 Å per cycle. Impurity content in the films was relatively small for a low temperature ALD process.
Slight surface modifications of TiO2 (“insignificant” at first glance), such as exposing to reducing or oxidizing agents and deposition of small amounts of a semiconductor material at the surface, may strongly affect the photoactivity of materials.
In this work, we have studied the applicability of Co(BTSA)2(THF) (BTSA = bis(trimethylsilyl)amido) (THF = tetrahydrofuran) in atomic layer deposition (ALD) of cobalt oxide thin films. When adducted with THF, the resulting Co(BTSA)2(THF) showed good volatility and could be evaporated at 55 °C, which enabled film deposition in the temperature range of 75-250 °C. Water was used as the co-reactant, which led to the formation of Co(II) oxide films. The saturative growth mode characteristic to ALD was confirmed with respect to both precursors at deposition temperatures of 100 and 200 °C. According to grazing incidence X-ray diffraction measurements, the films contain both cubic rock salt and hexagonal wurtzite phases of CoO. X-ray photoelectron
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.