Article

Low Temperature Atomic Layer Deposition of Nickel Sulfide and Nickel Oxide Thin Films Using Ni(dmamb)2 as Ni Precursor

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Abstract

Nickel(II) 1-dimethylamino-2-methyl-2-butoxide (Ni(dmamb)2) with water and hydrogen sulfide as oxygen and sulfur sources was employed in atomic layer deposition (ALD) of nickel oxide (NiO) and nickel sulfide (NiS) thin films. Both NiO and NiS thin films demonstrate temperature-independent growth rates per cycle of 0.128 nm/cycle and 0.0765 nm/cycle, at 130–150 °C and 80–160 °C, respectively. Comparison of two nickel-based thin film materials demonstrates dissimilar deposition features depending on the reactivity of the Ni precursor, i.e., Ni(dmamb)2 with anion sources provided by the water and hydrogen sulfide reactants. Difference in reactivity observed for NiO and NiS ALD processes is further investigated by density functional theory (DFT) simulations of surface reactions, which indicated that H2S demonstrate higher reactivity with surface-adsorbed Ni precursor than H2O. The material properties of ALD NiO and NiS thin films including stoichiometry, crystallinity, band structure, and electronic properties were analyzed by multiple experimental techniques, showing potential of ALD NiS as electrode or catalyst for energy-oriented devices.

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... The highest reports are 0.13−0.14 nm/cycle for a Ni(dmamb) 2 and H 2 O process 25 and, very recently, 0.2 nm/ cycle for a Ni(acac) 2 (TMEDA) and O 3 process. 26 However, both appear to exhibit fairly slow reaction kinetics. ...
... 28 The 200°C as-deposited ALD NiO films in this work exhibit optical properties (RI = 2.36 and E G = 3.78 eV) consistent with bulk NiO obtained from the flame-fusion method (RI = ∼2.36 to ∼2.45) 60,61 as well as thin film NiO obtained from ALD using Ni(dmamb) 2 + O 3 (RI = 2.35, E G = 3.7−3.8 eV) 53 and Ni(dmamb) 2 + H 2 O (E G = 3.52 eV), 25 oxidation of Ni metal films at temperatures >400°C (RI = 2.2−2.5, E G = 3.35−3.85 eV), 62 and nebulized spray pyrolysis (RI = 2.1−2.4, ...
Article
A novel atomic layer deposition (ALD) process for nickel oxide (NiO) is developed using a recently reported diazadienyl complex, Ni(tBu2DAD)2, and ozone. A window of constant growth per cycle is found between 185-200 °C at 0.12 nm/cycle, among the highest reported for ALD NiO. For films deposited at 200 °C, grazing-incidence x-ray diffraction indicates a randomly-oriented polycrystalline cubic NiO phase. X-ray photoelectron spectroscopy shows good agreement with bulk NiO reference spectra and no detectable impurities. Atomic force microscopy reveals low RMS roughness of 0.6 nm for an 18 nm thick film. The refractive index of 2.36 and an electronic bandgap of 3.78 eV, as determined by variable angle spectroscopic ellipsometry, are close to reported values for bulk and thin film NiO. Finally, fabricated Ag/NiO/n-Si/In heterojunction diodes shows a current-voltage asymmetry of 1.27x10⁴ at 2.3 V and ideality factor of 3.5, confirming the intrinsic p-type semiconducting behavior of transparent NiO.
... 75 According to Ko et al the high nickel content stems from the presence of metallic nickel in the films. 76 These films were shown to have high resistivity of 1.7Á10 7 Ω cm and a work function of 4.18 eV. 76 A work function of 4.3 eV has also been measured from films grown by a similar type of precursor, Ni(dmamp) 2 and water. ...
... 76 These films were shown to have high resistivity of 1.7Á10 7 Ω cm and a work function of 4.18 eV. 76 A work function of 4.3 eV has also been measured from films grown by a similar type of precursor, Ni(dmamp) 2 and water. 77 Recently, Holden et al reported an ALD process with Ni(DAD) and O 2 , resulting in films with a Ni/O ratio of 1.1 to 1.2, as measured by XPS. ...
Article
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Nickel oxide (NiOx), a p-type oxide semiconductor, has gained significant attention due to its versatile and tunable properties. It has become one of the critical materials in wide range of electronics applications, including resistive switching random access memory devices and highly sensitive and selective sensor applications. In addition, the wide band gap and high work function, coupled with the low electron affinity, have made NiOx widely used in emerging optoelectronics and p-n heterojunctions. The properties of NiOx thin films depend strongly on the deposition method and conditions. Efficient implementation of NiOx in next-generation devices will require controllable growth and processing methods that can tailor the morphological and electronic properties of the material, but which are also compatible with flexible substrates. In this review, we link together the fundamental properties of NiOx with the chemical processing methods that have been developed to grow the material as thin films, and with its application in electronic devices. We focus solely on thin films, rather than NiOx incorporated with one-dimensional or two-dimensional materials. This review starts by discussing how the p-type nature of NiOx arises and how its stoichiometry affects its electronic and magnetic properties. We discuss the chemical deposition techniques for growing NiOx thin films, including chemical vapor deposition, atomic layer deposition, and a selection of solution processing approaches, and present examples of recent progress made in the implementation of NiOx thin films in devices, both on rigid and flexible substrates. Furthermore, we discuss the remaining challenges and limitations in the deposition of device-quality NiO x thin films with chemical growth methods.
... Researchers have highlighted that the best band gap energy of metal chalcogenide is about 1.5 eV, indicating these films absorb a very broad range of the light spectrum. Literature showed that synthesis of nickel sulfide [Yue et al., 2014;Christine et al., 2017;Nan et al., 2014;Ko et al., 2018;Mgabi et al., 2014] and lead sulfide films [Ikhioya et al., 2017;Nair et al., 1992;Moe et al., 2017;Veena et al., 2017] have been deposited onto various substrates. For this reason, these elements were used to produce ternary compound in my project. ...
Article
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Currently, thin films have high potential for use in optoelectronic and solar cell applications due to appropriate band gap value. There are many deposition techniques have been used to prepare thin films including physical and chemical method. Chemical bath deposition technique was used to produce thin films. This technique has many advantages such as can control film thickness, quality of sample, and deposition rate. In this work, Ni3Pb2S2 films were deposited onto glass slide from aqueous solutions. Characterization of obtained films were investigated by using various tools. X-ray diffraction, atomic force microscopy and UV-visible spectrophotometer were employed to investigate the structure, topography and optical properties of films. Photovoltaic parameters were studied using a simulated AM1.5 Global spectrums. The obtained nanostructured thin films indicated band gap of 1.4 eV. Optical properties exhibited higher absorption in ultraviolet region, while lower absorption could be observed in infrared region. These ternary compounds indicated efficiency of 2.7 % based on power conversion efficiency testing.
... Researchers have highlighted that the best band gap energy of metal chalcogenide is about 1.5 eV, indicating these films absorb a very broad range of the light spectrum. Literature showed that synthesis of nickel sulfide [Yue et al., 2014;Christine et al., 2017;Nan et al., 2014;Ko et al., 2018;Mgabi et al., 2014] and lead sulfide films [Ikhioya et al., 2017;Nair et al., 1992;Moe et al., 2017;Veena et al., 2017] have been deposited onto various substrates. For this reason, these elements were used to produce ternary compound in my project. ...
Article
Full-text available
Currently, thin films have high potential for use in optoelectronic and solar cell applications due to appropriate band gap value. There are many deposition techniques have been used to prepare thin films including physical and chemical method. Chemical bath deposition technique was used to produce thin films. This technique has many advantages such as can control film thickness, quality of sample, and deposition rate. In this work, Ni3Pb2S2 films were deposited onto glass slide from aqueous solutions. Characterization of obtained films were investigated by using various tools. X-ray diffraction, atomic force microscopy and UV-visible spectrophotometer were employed to investigate the structure, topography and optical properties of films. Photovoltaic parameters were studied using a simulated AM1.5 Global spectrums. The obtained nanostructured thin films indicated band gap of 1.4 eV. Optical properties exhibited higher absorption in ultraviolet region, while lower absorption could be observed in infrared region. These ternary compounds indicated efficiency of 2.7 % based on power conversion efficiency testing.
... DFT calculations were performed to obtain insights on the mechanistic details of the surface reactions determining the composition of ALD Sn(O,S) (Fig. 11). Depositions of sulfide materials via ALD often show more facile reaction compared to ALD oxide using the same precursor [47]. Furthermore, it is known that exchange reactions of the surface functional groups, e.g., *OH and *SH, may occur during multicomponent ALD using supercycles [48]. ...
Article
Sn(II) dimethylamino-2-methyl-2-propoxy (Sn(dmamp)2) with water and hydrogen sulfide as oxygen and sulfur sources was employed in atomic layer deposition (ALD) of composite tin oxysulfide thin films abbreviated by Sn(O,S) made up of tin oxide (SnO) and tin sulfide (SnS) thin films employed as end members in addition to tin oxide and tin sulfide. Both SnO and SnS thin films demonstrate temperature-independent growth rates per cycle of 0.042nm/cycle and 0.056 nm/cycle, at 100–160 °C and 100–130 °C, respectively. Comparison of two tin-based thin film materials demonstrates dissimilar deposition features depending on the reactivity of the Sn precursors, i.e., Sn(dmamp)2 with anion sources provided by the water and hydrogen sulfide reactants. Density functional theory (DFT) calculations show that surface exchange reaction between *OH and *SH groups determine preference of S incorporation in the Sn(O,S) thin films. The material properties of ALD-based SnO, SnS, and Sn(O,S) thin films were characterized in terms of composition, stoichiometry, crystallinity, band structure, and electronic properties, demonstrating the potential of ALD SnO and SnS as p-type channel materials for transparent electronics.
... Although ALD offers so many advantages, the ALD of NiO film is not well developed. Over the past two decades, a number of ALD processes for the preparation of NiO films have been developed using different combinations of nickel and oxygen precursors, including Ni(Cp) 2 (Cp = cyclopentadienyl) [20][21][22][23][24][25], Ni(MeCp) 2 (MeCp = methylcyclopentadienyl) [26,27], Ni(EtCp) 2 (EtCp = ethylcyclopentadienyl) [24,28,29], Ni(dmamp) 2 (dmamp = 1-dimethylamino-2-methyl-2-propanolate) [30], Ni(dmamb) 2 (dmamb = 1-dimethylamino-2-methyl-2butanolate) [31][32][33][34][35], Ni(acac) 2 (acac = acetylacetonate) [36][37][38], Ni (apo) 2 (apo = 2-aminopent-2-en-4-onato) [36], Ni(dmg) 2 (dmg = dimethylglyoximato) [36], Ni(thd) 2 (thd = 2,2,6,6-tetramethylheptane-3,5-dionato) [39], and Ni(amd) 2 (amd = amidinate) [40][41][42] in combination with O 3 , water (H 2 O), hydrogen peroxide (H 2 O 2 ), or oxygen plasma. However, just as most reported ALD processes for the preparation of metal-based films are limited by a low growth rate (such as less than 1.0 Å/cycle) [18,[43][44][45], and this limitation also applies to the ALD of NiO films. ...
Article
In this study, we described an atomic layer deposition (ALD) process for the preparation of nanoscale nickel oxide (NiO) films with high growth rate by using a combination of nickel(II) diketonate–diamine (Ni(acac) 2 (TMEDA), TMEDA = N,N,N′,N′-tetramethyl-ethylenediamine) and ozone (O 3 ). Typical self-limiting film growth behavior was observed between 200 and 275 °C, and growth saturation with respect to both precursor pulse time was verified. The chemical composition, crystalline phase, and surface morphology of the films were studied using X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy. All the results confirmed that the ALD process occurred with high growth rate of approximately 2.0 Å/cycle and resulted in high-quality, smooth films.
Chapter
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Nickel sulfide (NiSx) was grown by atomic layer infiltration using bis(dimethylamino-2-methyl-2-butoxo)nickel(II) [Ni(dmamb)2] and hydrogen sulfide (H2S) as a metal precursor and a sulfur source. The steady-state growth rate of the film was 3.7 Å/cycles at 160–190 °C which was much faster compared to those by conventional atomic layer deposition method (<0.7 Å/cycles). This nickel sulfide thin films were characterized by taking X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction, and hall measurements. The deposited films on Si wafer was single-phase polycrystalline with multiple domains. The NiSx film grown on fluorine-doped tin oxide (FTO)-coated glass was applied to a counter electrode in dye-sensitized solar cells, which performed a high catalytic activity for the reduction of I3⁻ to I⁻ and the comparable cell efficiency of 7.12% with cells using conventional Pt-coated FTO counter electrode. © 2019 The Korean Society of Industrial and Engineering Chemistry
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