Precise positioning of metallic nanostructures on semiconductor surfaces is important for applications such as photovoltaics, photoelectrocatalysis, metal interconnects, sensing platforms, and many others. In this paper, we demonstrate the utilization of self-assembling diblock copolymer monolayer films, made up of polystyrene-block-poly(2- or 4-vinylpyridine) (PS-b-P2VP or PS-b-P4VP), to spatially direct an aqueous metal reduction reaction on semiconductor surfaces, a process we call galvanic displacement. The diblock copolymer forms hexagonal arrays of spherical micelles consisting of a P2VP or P4VP core surrounded by a PS corona. Two approaches were developed, termed method 1 and method 2, to deliver metal ions to the semiconductor interface in a spatially defined manner utilizing the diblock template. In method 1, a metal complex preloaded into the P4VP cores is spontaneously reduced on the surface to form hexagonally ordered metallic nanoparticles whose structures mirror the parent polymer templates....

Block Copolymer Templated Chemistry for the Formation of Metallic Nanoparticle Arrays on Semiconductor Surfaces

Indium oxide thin films are deposited via plasma-enhanced atomic layer deposition (PEALD) to exploit their potential as a semiconductor in high mobility thin-film transistors (TFTs), which are suitable for fast driving applications such as high resolution displays. The films are successfully grown by the reaction between an Et2InN(SiMe3)2 liquid precursor and oxygen plasma at temperatures ranging from 100 °C to 250 °C giving a saturated growth rate value of ∼1.45 A per cycle at the ALD window with precisely controlled thickness and uniformity. The plasma reaction enhances the film growth rate and changes the electrical properties of the films. Depending on the substrate temperatures, each film has a different chemical composition, thereby showing different electrical characteristics. Indium oxide films grown by PEALD show a lower carrier density of ∼4 × 1019 cm−3 than those prepared by thermal ALD due to the reactive oxygen plasma source in the former. Offering the precise control of thickness and high quality of indium oxide grown by PEALD, and with a proper post thermal-annealing and passivation process, the possibility of exploiting the potential of semiconductor characteristics of indium oxide is verified from bottom-gate coplanar structured TFTs, which exhibit a high mobility as high as 39.2 cm2 V−1 s−1, a turn-on voltage value of −1.18 V, and a sub-threshold voltage of 0.27 V dec−1 in a linear region. On the basis of this outstanding performance, the PEALD-InOx TFTs developed in this study would be suitable for diverse microelectronic devices.

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High mobility polycrystalline indium oxide thin-film transistors by means of plasma-enhanced atomic layer deposition

Influence of sol concentration on CdO nanostructure with gas sensing application

Spontaneous crystal coalescence enables highly efficient perovskite solar cells

Ultrathin silver films have been deposited on glass and oxide-coated glass using filtered cathodic arc deposition and, for comparison, magnetron sputtering. The energetic differences between these deposition methods lead to initially different film properties. Silver films made by cathodic arc deposition show an earlier onset of island coalescence, indicating a lower aspect ratio than islands produced by evaporation and sputtering. However, the as-deposited films are thermodynamically unstable, exhibiting changes on a timescale of minutes. While films of islands tend to increase their sheet resistance with time, the sheet resistance of contiguous films shows a decrease. Both effects can be explained by silver mobility driven to minimize film and interfacial energy.

/pdf/coalescence-of-nanometer-silver-islands-on-oxides-grown-by-ohtnscdq5z.pdf

Coalescence of nanometer silver islands on oxides grown by filtered cathodic arc deposition

Effect of annealing temperature on the evolution of structural, microstructural, and optical properties of spin coated ZnO thin films

Zinc oxide (ZnO) thin films were deposited on glass substrates through spin coating technique. Zinc acetate dihydrate, monoethanolamine and 2-methoxyethanol were used as the starting material, stabilizer and solvent, respectively. The effect of precursor concentration on the structural, optical and electrical properties of ZnO thin films is investigated. The X-ray diffraction studies reveal that all the films are polycrystalline in nature with preferred (002) orientation with crystallite size ranging from ~25 to 32 nm. Atomic force microscopy images infer the columnar growth of the films. From the optical measurements it was found that there was a marginal decrease in the band gap energy with increase in molarity up to 0.7 M. Optical constants and thickness of the films were found with the help of Swanepoel envelope method and were verified through ellipsometric measurements. Electrical resistivity of the grown films was found to be in the range 29–244 Ω cm, with a lowest value obtained for the films grown at 0.7 M. Carrier concentration of the grown films has also followed a similar trend. On the other hand, the Hall effect mobility (~400 cm2/Vs) was highest for the films grown at 0.7 M. Such high values make these films potential candidates for photovoltaic and display applications.

Dependence of solution molarity on structural, optical and electrical properties of spin coated ZnO thin films

Structural studies on silver cluster films deposited on softened PVP substrates

Results of the investigations carried out on particulate silver films, deposited at a rate of 0.4 nm s-1 on poly(4-vinylpyridine) coated substrates held at temperatures in the range 440-490 K in a vacuum of 8 × 10-6 Torr are reported in this paper. A morphological study by scanning electron microscopy and x-ray diffraction was further confirmed by optical absorption studies. The shift in the plasmon resonance towards longer wavelength is ascribed to polymer-metal particle interactions. Electrical resistances immediately after deposition and at room temperature show a regular dependence on the thickness for the films in the temperature range studied. The films deposited at lower substrate temperatures show a lower negative temperature coefficient of resistance when compared to films deposited at higher substrate temperatures. X-ray photoelectron spectroscopy studies indicate the formation of a sub-surface particulate structure at higher substrate temperatures.

https://iopscience.iop.org/article/10.1088/0022-3727/32/18/303/pdf

K. Mohan Rao

Papers

Effect of annealing temperature on the evolution of structural, microstructural, and optical properties of spin coated ZnO thin films

Dependence of solution molarity on structural, optical and electrical properties of spin coated ZnO thin films

Structural studies on silver cluster films deposited on softened PVP substrates

Preparation and characterization of silver particulate structure deposited on softened poly(4-vinylpyridine) substrates

Aging studies on discontinuous silver films in ultrahigh vacuum