The morphology and texture of Cu nanorod films grown by controlling the directional flux in physical vapor deposition

We report the creation of unusual biaxial textures in Cu nanorod films, through the control of the incident vapor flux during oblique angle deposition. High-density twin boundaries were formed using a periodic azimuthal swing rotation of the substrate while the incident angle of the Cu flux was fixed at 85° with respect to the surface normal. In contrast, depositions on stationary substrates resulted in nanorod films with a much lower density of twinned crystals. From transmission electron microscopy and x-ray pole figure analysis, the nanorod axis was shown to coincide approximately with the [Formula: see text] crystallographic directions. We also observed the branching of these nanostructures into 'nanotrees'. This branching was attributed to the creation of edge dislocations during the deposition and was particularly prevalent for the case of swing rotation. The mechanisms for the development of texture, twinning, and branching in these nanostructures are discussed.     

Wavy surface nanostructures formed in amorphous silicon films by sputtering with nitrogen ions

Wavy nanostructures are formed on the ion-bombarded surface of single-crystal and amorphous silicon films prepared by various methods. The period and depth of this structure have been determined as functions of the angle of incidence and the energy of nitrogen ions used for the surface sputtering. A comparative analysis of SEM images of the wavy surface nanostructures on various silicon films has been performed using a two-dimensional Fourier transform. The films of amorphous silicon obtained by electron beam deposition and magnetron sputtering techniques are closest to single-crystal silicon films with respect to the wavy surface nanostructure formation.     

Nanostructure engineering in porous columnar thin films: recent advances

Glancing angle deposition (GLAD) is a physical vapour deposition method used to fabricate highly functional thin films with an engineerable columnar morphology. Recent developments in GLAD technology have produced columnar nanostructures of increased complexity, including periodic, nanofibrous, perforated, and graded porosity thin films for use in applications ranging from sensors and actuators to optical filters, microfluidics, and catalysis. A brief review of GLAD methodology and historical developments is followed by a discussion of the latest developments in this field.     

Dünne Schichten durch Deposition unter streifenden Einfall

Micro‐ and nanostructured thin films by Glancing angle deposition Physical vapour deposition under conditions of obliquely incident flux and limited adatom diffusion results in films with a columnar microstructure. These columns will be oriented toward the vapour source. An additional substrate rotation can be used to sculpt the columns into various morphologies (slanted and vertical posts, chevrons, screws or spirals). With this glancing angle deposition (GLAD) technique can prepared porous thin films with engineered structures from a variety of dielectric, semiconducting and metallic materials. The paper presents the In this paper the physical fundamentals of the GLAD technique are introduced, the production of micro‐ and nanostructures of different morphology on non‐patterned and patterned substrates is demonstrated and some possible applications of this new deposition technique are introduced.     

纳米结构的倾斜角度沉积及性能优化

纳米材料发展的关键是纳米结构的制备、形貌调控和性能优化.倾斜角度沉积是以较大的角度(大于75°)倾斜入射沉积薄膜,通过控制沉积参数,得到具有特殊形貌纳米结构的方法,具有适用范围广,操作便捷,制备的薄膜面积大、纯度高、结构规整等特点,是一种理想的制备纳米材料的方法.本文介绍了采用倾斜角度沉积技术制备氧化铪抗反射薄膜和银基表面增强拉曼基底,详细分析了该方法的参数调控对纳米结构的形貌和性能的影响,并指出将倾斜角度沉积与其他先进技术相结合(以原子层沉积为例),可进一步优化纳米结构的性能,提高倾斜角度沉积的使用范围.     

High absorbing CuInS<Subscript>2</Subscript> thin films growing by oblique angle incidence deposition in presence of thermal gradient

Oblique angle deposition technique can generate nanostructures and has attracted the interest of many researchers. In this article we use this technique to investigate the physical properties of obliquely evaporated CuInS₂ films deposited onto substrates submitted to a thermal gradient. We show that the correlation between the obliquely angle deposition and the thermal gradient leads to an improvement in the optical properties of the films. Indeed high absorption coefficient (10⁵–3.10⁵ cm⁻¹) in the visible range and near-IR spectral range are reached for the small incident angles. Scanning electron microscopy shows that the films had a microstructure with columns that are progressively inclined as the incident angle was increased.     

Effect of nanostructures formed by oblique co-deposition on transient catalytic reactions

We investigated the effects of nanostructures of obliquely co-sputter-deposited thin films in terms of catalytic properties using pulses of reactant molecules as probes. Pt-Al₂O₃ thin films were fabricated on a Si substrate by simultaneous oblique deposition. The films had columnar structures that grew perpendicular to the substrate. We observed the behavior of NO reduction by H₂ with a specially designed apparatus employing pulse valves for the injection of reactant molecules onto the thin film surface and a time-of-flight mass spectrometer to measure plural products. The obliquely co-deposited films, consisting of columnar nanostructures, showed higher NO reduction activity over a wide range of temperatures than the normally co-deposited films, consisting of uniform structures. The yield of N₂ exceeded that of NH₃ and N₂O for both structures in the high temperature range, whereas the yield of N₂O was more significant for the structures with columns than those without columns at low temperatures. Subtle change of the nanometer-scale structures with the deposition angle was clearly discriminated from the viewpoint of transient catalytic activity.     

Wettability property of CNT-graphene like film deposited by microwave plasma enhanced vapor deposition technique

Wettability property of carbon nano-tubes (CNT)-graphene like films have been investigated. In this work, we have studied the wettability of CNT-graphene like film deposited on Ni substrate by Microwave Plasma Enhanced vapor deposition Technique (MWPECVD). Compared to the water contact angles of 77.8° for bare Ni substrate, the water contact angle of the CNT-graphene like hybrid films is found to be 128.4°. The nanostructures have been deposited at fixed pressure of 20?Torr with different temperature of 500, 600 and 700?°C. The results indicate that wettability properties of nano-structure can be tailored, significantly. The solid surface energy (SE) of composite films was estimated using contact angle measurements. The wettability of CNT-graphene has been studied first time in film form.     

Evaporated nanostructured Y2O3:Eu thin films

Europium-doped yttrium oxide (Y2O3:Eu) is a well-known luminescent material that in recent years has been studied in thin-film form. However, to date there has not been a great effort put into altering the nanostructure of these films. A thin-film deposition technique called glancing angle deposition allows for a high degree of control over the nanostructure of the thin film, resulting in thin films with nanostructure geometries ranging from chevron and post to helix. Glancing-angle deposition was used to make europium-doped yttrium oxide thin films with slanted-post nanostructures. Portions of the films were annealed in air at 850 degrees C for 10 hours following deposition. Scanning electron microscopy was used to characterize the nanostructures of the films, while UV laser excitation was used to characterize the photoluminescence properties of the films. The annealed samples exhibited increased photoluminescent responses compared to unannealed samples; however, the porous nanoscale geometry of the films was unaffected. In order to optimize the photoluminescence properties of the films, both the partial pressure of oxygen during film deposition and the level of europium doping in the source material used were varied. Films fabricated from the source material with a greater amount of europium doping had larger photoluminescent responses, while the optimal partial pressure of oxygen during electron-beam evaporation was found to be less than 1.0 x 10(-4) torr.     

Solution-phase deposition and nanopatterning of GeSbSe phase-change materials

Chalcogenide films with reversible amorphous-crystalline phase transitions have been commercialized as optically rewritable data-storage media, and intensive effort is now focused on integrating them into electrically addressed non-volatile memory devices (phase-change random-access memory or PCRAM). Although optical data storage is accomplished by laser-induced heating of continuous films, electronic memory requires integration of discrete nanoscale phase-change material features with read/write electronics. Currently, phase-change films are most commonly deposited by sputter deposition, and patterned by conventional lithography. Metal chalcogenide films for transistor applications have recently been deposited by a low-temperature, solution-phase route. Here, we extend this methodology to prepare thin films and nanostructures of GeSbSe phase-change materials. We report the ready tuneability of phase-change properties in GeSbSe films through composition variation achieved by combining novel precursors in solution. Rapid, submicrosecond phase switching is observed by laser-pulse annealing. We also demonstrate that prepatterned holes can be filled to fabricate phase-change nanostructures from hundreds down to tens of nanometres in size, offering enhanced flexibility in fabricating PCRAM devices with reduced current requirements.     

Film morphology modification in ion-assisted glancing angle deposition

Porous structured films grown with the glancing angle deposition technique have been widely studied for thin film optical device applications. We report the use of ion assistance to modify the structural and optical properties of porous silicon dioxide and titanium dioxide columnar thin films grown at deposition angles of 70° and 85°. Optical characterization studies show that tilted columnar structures will undergo an increase in tilt angle and film density with increasing ion dose. These two trends contrast with unassisted films where film density and column tilt angle are primarily controlled by the deposition angle. Thus, a regime of film structures simultaneously exhibiting high film density and large column tilt angle is enabled by incorporating an ion-assisted process. The phisweep substrate motion algorithm for minimizing columnar anisotropy used in conjunction with ion-assisted deposition provides additional control over film morphology and expands the utility of this modified fabrication process.     

Angle dependent optical properties of polymer films with a biomimetic anti-reflecting surface replicated from cylindrical and tapered nanoporous alumina

Anodic porous alumina nanostructures have been fabricated with tapered and cylindrical pores with a spacing of 100 and 200 nm and depth of 180-500 nm. The porous nanostructures were replicated into polymer films to create a moth-eye anti-reflecting surface by a roll-to-roll UV replication process. The angle dependent optical transmission of the resulting polymer films exhibited up to a 2% increase in transmission at a normal angle and up to a 5% increase in transmission at a 70° angle of incidence to an equivalent film with a surface replicated from polished aluminum. No significant difference was observed between the optical performance of moth-eye surfaces formed from cylindrical and tapered nano-pores.     

Nanocrystallisation of TiO2 induced by dense electronic excitation

Amorphous thin films of TiO₂ grown by pulsed laser deposition and thermal evaporation method are irradiated by swift heavy ions. Nanocrystallisation is induced by dense electronic excitation in films grown by both the methods. The surface morphology is studied by atomic force microscopy (AFM). Hillocks-like nanostructures emerge on the surface of irradiated films. Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy are carried out for phase identification. Optical characterisation is done by UV-vis absorption spectroscopy. Increase in bandgap after irradiation indicates quantum confinement of nanoparticles. Mechanism behind amorphous to nanocrystalline phase transition is discussed.     

Small Molecule Organic Nanostructures—Fabrication and Properties

Organic materials are of great interest for the development of low cost electronic and optoelectronic devices. Although majority of research on organic materials is concerned with synthesis of novel compounds and organic thin films, organic nanostructures are attracting increasing interest in recent years. We briefly review different growth methods of organic nanostructures, which can be roughly divided into vapor deposition methods and self-assembly techniques in solution. Then we highlight some interesting properties of organic nanostructures, as well as possible applications, includinf field emission, electronic and optoelectronic devices.     

Cu2ZnSnS4 thin films and nanowires prepared by different single-step electrodeposition method in quaternary electrolyte

We investigated the effect of single-step electrodeposition methods for the fabrication of CZTS thin films as solar cell absorber layer. For deposition of CZTS thin films, a potentiostatic method and a pulsed potential electrodeposition method were examined. Near stoichiometric CZTS thin films were prepared by potentiostatic deposition method. On the other hands, the samples deposited by pulsed potential method showed wire-like CZTS nanostructures. The nanowires were composed of the Cu and S element mainly and included Zn and Sn microelements. From these results, we realized that the electrodeposition methods strongly affect the structural and compositional characteristics of as-deposited CZTS thin films.     

Atomic layer deposition of TiO(2) nanostructures for self-cleaning applications

Nanostructured titanium dioxide (TiO(2)) porous films and nanotube arrays were prepared by atomic layer deposition (ALD) on porous anodic alumina (PAA) templates. The nanostructures were characterized by FESEM and XRD to investigate the structural and crystallographic characteristics. They were then evaluated as self-cleaning surfaces by comparing their photocatalytic activities and photoinduced hydrophilic property under 365?nm illumination. The?nanostructures showed photocatalytic activities and photoinduced hydrophilicity, with nanostructures showing enhanced photoactivity when compared to planar structures. Both photocatalytic and photoinduced hydrophilic properties were strongly affected by the dimension and morphology of the nanostructures. The prepared nanostructures could have potential application as self-cleaning surfaces.     

Obliquely sputtered TbFe giant magnetostrictive films with in-plane anisotropy

We have found that in-plane magnetostriction characteristics at low fields can be greatly improved by an oblique sputtering technique. We report a study of deposition of in-plane anisotropic TbFe giant magnetostrictive films by dc magnetron oblique sputtering, including the influences of deposition angle on TbFe film magnetic and magnetostrictive performances. The in-plane magnetization of TbFe films at 1600 kA/m is drastically increased with a change of deposition angles from 90/spl deg/ to 15/spl deg/. Magnetic domain structures explored by magnetic force microscopy indicate that the easy magnetization directions of the films can be gradually changed from perpendicular to the film plane at sufficiently shallow deposition angles. The in-plane magnetostrictive coefficients /spl lambda/ at 16 kA/m also can be increased by decreasing the deposition angles from 90/spl deg/ to 15/spl deg/. The significant variation in the in-plane magnetic and magnetostrictive performances can be explained by the decrease of perpendicular anisotropy of TbFe films.     

Superhydrophobic polymer films via aerosol assisted deposition — Taking a leaf out of nature's book

Aerosol assisted deposition of three sets of polymer films based on commercially available resins was achieved on various substrates. The films were characterised using a range of methods, including water contact and slip angle to determine water repellent properties. The aerosol assisted deposition inside the chemical vapour deposition reactor was unique in generating a highly rough superhydrophobic surface with water contact angles up to 170°. During the deposition process, two of the polymers were cured resulting in the development of high surface morphology. It was observed that the polymer that did not cure did not develop such a rough surface resulting in a lower water contact angle (∼ 99°). The superhydrophobic films had a Cassie-Baxter type wetting with water failing to penetrate the surface porosity, water spraying on the surface would bounce off. These films had exceptionally low slide angles of ca 1-2° from the horizontal.     

Magnetic properties of thin films prepared by continuous vapor deposition

Magnetic thin films deposited by the oblique incidence evaporation are considered to have excellent characteristics for high density recording medium. The magnetic properties and microstructures of these films prepared continuously with a roll coater have been investigated. In continuous vapor deposition, two different modes of deposition processes are considered, corresponding to substrate running direction. The HIN (high incidence nucleation) direction implies that deposition initiates at higher incidence angle and shifts to lower incidence angle. The LIN (low incidence nucleation) direction is the opposite. Hc and Ir/Is of the films by HIN direction have larger values than those by LIN direction in the same region of incidence angle. According to TEM micrographs of thin films by HIN direction, it is observed that elongated nucleation is taken place in higher incidence angle direction and subsequently grown in same direction.