The measurement of thermal conductivities using the photothermal deflection method for thin films with varying thickness

This study considers non-contact methods that obviate the causes of measurement error, such as thermal contact resistance and the unnecessary destruction of samples. Among the methods, the photothermal deflection method has been adopted and developed to measure the thermal conductivities of thin-film materials. To apply the developed method for thin films, bi-layered materials are manufactured by depositing the film on Corning 7740 glass plates. The study also investigates the optimal modulation frequency, as related to the thermal diffusion length of the sample, for measuring thermal conductivities of thin films.. Aluminum, TiO₂, and Si₃N₄ films with micro/nanometer thickness were selected as the objects for measurement; the thermal conductivities of these films were experimentally measured. Samples of thickness ranging from 1 μm to 200 nm were prepared to measure the variations in thermal conductivities with thickness. It was observed that the thermal conductivity in submicroscale films decreased as the thickness was reduced.     

Cold-stage microscopy system for fast-frozen liquids

The least artifact-laden fixation technique for examining colloidal suspensions, microemulsions, and other microstructured liquids in the electron microscope appears to be thermal fixation, i.e., ultrafast freezing of the liquid specimen. For rapid-enough cooling and for observation in TEM/STEM a thin sample is needed. The need is met by trapping a thin layer ( approximately 100 nm) of liquid between two polyimide films ( approximately 40 nm thickness) mounted on copper grids and immersing the resulting sandwich in liquid nitrogen at its melting point. For liquids containing water, polyimides films are used since this polymer is far less susceptible to the electron beam damage observed for the commonly used polymer films such as Formvar and collodion in contact with ice. Transfer of the frozen sample into the microscope column without deleterious frost deposition and warming is accomplished with a new transfer module for the cooling stage of the JEOL JEM-100CX microscope, which makes a true cold stage out of a device originally intended for cooling specimens inside the column. Sample results obtained with the new fast-freeze, cold-stage microscopy system are given.     

Interfacial effect on thermal conductivity of diamond-like carbon films

Diamond-like carbon (DLC) has been of interest as a promising coating for protection and insulating layer in micro-electromechanical systems due to high hardness, wear resistance, transparency in IR range, chemical inertness and biocompatibility. The interfacial effect on thermal transport is studied for DLC films deposited on Al₂O₃ substrates with an ion gun method. Thermal conductivity of DLC thin films is measured with a 3ω method. DLC films show the thickness-dependent thermal conductivity, which is understood with the interfacial thermal resistance between DLC thin film and Al₂O₃ substrate. The interfacial thermal resistance and thermal conductivity of bulk DLC are determined with the measured thickness-dependent thermal conductivity of DLC films.     

LR White sections as slot grid support films for transmission electron microscopy

The utility of LR White sections as slot grid support films for the examination of thin resin‐embedded tissue sections by transmission electron microscopy was investigated and compared with traditional formvar‐carbon films. Throughout a variety of staining procedures, which involved the use of organic solvent, oxidizing agents, strong acid and prolonged incubation, LR White support films remained intact and the attached tissue sections remained adherent. By contrast, complete loss of formvar‐carbon support films occurred in 25% of preparations during routine staining with aqueous reagents. This loss increased to 62% following staining with either alcoholic or oxidizing and acidic stains, and to 66% following prolonged (immunohistochemical) staining. Tissue contrast, ultrastructural detail and immunohistochemical staining intensity were comparable between sections on the two types of support film. The use of LR White sections as support films for slot grids represents a quick, cheap, simple and robust alternative to traditional support films and, furthermore, requires no carbon coating     

The Development and Use of Thin Film Thermocouples for Contact Temperature Measurement

A procedure was developed for producing thin film thermocouples (TFTC) on the contact surface of sliding mechanical components. The thermocouple devices were made from thin films of vapor-deposited copper and nickel. The measuring junctions of the thermocouples were approximately 2 μm thick and between 80 μm and 300 μm across. The TFTC devices were found to have extremely rapid (< 1 μS) response to a sudden temperature change and did not significantly disturb the heat flow from the sliding contact. It was found necessary to sandwich the TFTC between thin films of a hard, non-conducting ceramic (Al₂O₃ in the current work) to insulate the thermocouple electrically from the substrate and protect it during sliding.

Thin film thermocouple devices were applied to the measurement of sliding surface temperatures in two cases, oscillatory dry sliding of a polymer pin on a flat surface, and uni-directional dry sliding of a ring over a flat pin surface. Results from the tests verified theoretical predictions.     

Preparation of flat carbon support films

Wrinkling of carbon support films is known to limit the resolution of electron microscopy images of protein two-dimensional crystals. The origin of carbon wrinkling during preparation of the support films was investigated by reflected light microscopy. We observed that carbon films go through several states during their preparation. While dried carbon films have a tendency to be wrinkled, a flat state is observed transiently before complete drying. This state could be stabilized by the addition of sugars or tannic acid to the embedding medium. An alternative method for preparing flat carbon films was developed, in which a sandwich is formed by two symmetrical carbon films positioned on both sides of a grid. The formation of sandwiched carbon films was facilitated by the use of grids with thin bars. The carbon sandwich films were flat, stable, and easily and reproducibly prepared.     

A staining syringe for multiple em grids

In the EM-routine, the thin sections are usually attached onto round copper grids. The sections on these EM-grids are then stained either with a quite expensive automatic staining apparatus or by transporting the grids by hand from solution to solution. Here we will present a simple, inexpensive and truly reliable apparatus for staining and handling grids.     

Morphological properties of Ag₂SeTe nano thin films prepared by thermal evaporation

Semiconducting silver selenide telluride (Ag₂SeTe) thin films were prepared with different thicknesses onto glass substrates at room temperature using thermal evaporation technique. The structural properties were determined as a function of thickness by X‐ray diffraction exhibiting no preferential orientation along any plane; however, the films are found to have peaks corresponding to mixed phase. The morphology of these films was studied using scanning electron microscope and atomic force microscopy respectively, and is reported. The morphological properties are found to be very sensitive to the thin film thickness. The composition of the films is also estimated using energy dispersive analysis using X‐rays and are also reported.     

Optimum film thickness of thin metallic coatings on silicon substrates for low load sliding applications

The frictional behaviour of thin metallic films on silicon substrates sliding against 52100 steel balls is presented. The motivation of this work is to identify an optimum film thickness that will result in low friction under relatively low loads for various metallic films. Dry sliding friction experiments on silicon substrates with soft metallic coatings (silver, copper, tin and zinc) of various thickness (1–2000 nm) were conducted using a reciprocating pin-on-flat type apparatus under a controlled environment. A thermal vapour deposition technique was used to produce pure and smooth coatings. The morphology of the films was examined using an atomic force microscope, a non-contact optical profilometer and a scanning electron microscope. Following the sliding tests, the sliding tracks were examined by various surface characterization techniques and tools. The results indicate that the frictional characteristics of silicon are improved by coating the surface with a thin metallic film, and furthermore, an optimum film thickness can be identified for silver, copper and zinc coatings. In most cases ploughing marks could be found on the film which suggests that plastic deformation of the film is the dominant mode by which frictional energy dissipation occurred. Based on this observation, the frictional behaviour of thin metallic coatings under low loads is discussed and friction coefficients are correlated with an energy based friction model.     

Phospholipid,Nature's own slide and cover slip for cryo-electron microscopy

Thin films of surface-active compounds, with or without particulate material, can be obtained by immersing and withdrawing a bare specimen grid from a solution/suspension of the compound. Immediately after withdrawing the grid, thinning of the film starts. Thinning is initially powered by gravity and capillary forces and will proceed in thin films (< 100 nm) driven by intermolecular forces until the London-van der Waals attractive forces come to an equilibrium with electrostatic repulsion of similarly charged surfaces of the film. With small unilamellar vesicles prepared from the phospholipid dimyristoyl phosphatidyl choline (DMPC) the draining behaviour of these films was studied by cryo-electron microscopy. Small unilamellar vesicles were observed within the film as well as the coalescence of these vesicles into sheets (‘leaky’ membrane fusion). Sheets dominate the images when films are allowed to drain for longer periods (>3min). Thin films were formed on grids from catalase crystals suspended in a DMPC suspension and vitrified by cooling. High-resolution information was obtained by electron diffraction at low temperature and under low-dose conditions from catalase crystals surrounded by small vesicles as well as from catalase crystals surrounded by sheets of DMPC. In the latter case the water content drops from 99% (DMPC in small vesicles) to less than 30% (DMPC in sheets) during draining. Ferritin was added to a DMPC suspension and thin films were prepared and vitrified. After prolonged draining ferritin molecules were deposited in layers with a stepwise increase in thickness. Draining of thin films has thus a dehydrating effect as well as a sorting and ordering effect. These effects must be considered when using surface-active compounds at air-water interfaces as a slide and cover slip for electron microscopy.     

Phase separation as a basis for the formation of light-emitting silicon nanoclusters in SiO x films irradiated with swift heavy ions

This paper presents a study of the effect of swift heavy Xe ions of energy 130–167 MeV at doses of 10¹²–10¹⁴ cm^?2 and Bi ions of 700 MeV at doses of 3·10¹²–3·10¹³ cm^?2 on films of stoichiometric thermal silicon dioxide, silicon dioxide films with ion-implanted excess silicon, and SiO _x films with the stoichiometric parameter x varying from 0 to 2. According to electron microscopy and Raman spectroscopy data, irradiation with the swift heavy ions resulted in the formation of silicon nanoclusters. The luminescence spectra depended on the size, number, and structure of the Si nanoclusters formed. Their size can be controlled by varying both the effect parameters (primarily, the ion energy loss per unit length of the track) and the stoichiometric composition of the films.     

Modeling the formation of silicon nanoclusters during annealing SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> layers

The mechanism of formation of silicon nanoclusters in layers of nonstoichiometric composition is studied by Monte Carlo simulation. Interest in silicon nanoclusters (Si-nc) coated with an oxide layer is due to their applications in modern optoelectronics and nanoelectronics. A lattice Monte Carlo model is proposed to study atomic processes in the Si-SiO₂ system. The formation of silicon nanoclusters during annealing of single SiO layers and SiO₂-SiO-SiO₂ layered structures is studied. Along with the diffusive motion of particles, the model takes into account the formation and collapse of mobile molecules of silicon monoxide. It is shown that accounting for transport of silicon under high-temperature annealing due to the motion of SiO accelerates the formation of Si-nc. Dependences of the size of nanoclusters on temperature, annealing time, and the composition of the SiO _x layer are obtained. It is found that annealing of silica films containing layers of nonstoichiometric composition can lead to the formation of silicon nanoclusters or cavities.     

Parameters affecting specimen flatness of two-dimensional crystals for electron crystallography

The flatness of two-dimensional (2D) crystals on the support film is a critical factor in protein electron crystallography. The influence of the carbon support film and of different grid makes and materials on flatness was investigated, using as a criterion the sharpness of diffraction spots perpendicular to the tilt axis of electron diffraction patterns of purple membrane tilted in the microscope at 45 degrees. In a quantitative test, carbon film that had been evaporated without sparks forming gave a much larger proportion of flat crystals than "sparked" carbon. Titanium grids were superior to copper, probably because they introduce less cryo-crinkling of the carbon film when the sample is cooled to liquid nitrogen temperature, as their thermal expansion coefficient is closer to that of carbon. While the molybdenum grids from Plano were unsuitable for data collection because of their tendency of break the carbon, molybdenum grids from Pacific GridTech gave a much larger yield of flat crystals than the titanium grids. Scanning electron microscope images of the grids as supplied by the manufacturer showed that the Plano grids had very narrow and irregular grid bars, while the Pacific GridTech grids were very smooth with a large surface-to-hole ratio.     

The Tribological Chemistry of Novel Triazine Derivatives as Additives in Synthetic Diester

Two novel triazine derivatives 2-tris(2-ethylhexyl)-3,3′,3″-(1,3,5-triazine-2,4,6-triyl)-tris(sulfanediyl)tripropanoate (TE TST) and 2-ethylhexyl-3-(4,6-dimercapto-1,3,5-triazin-2-ylthio) propanoate (EDTYP) were synthesized. Their tribological properties in synthetic diester were evaluated using a four-ball tribometer, and the thermal films and tribofilms were investigated using X-ray absorption near-edge structure (XANES) spectroscopy. The copper corrosion-inhibiting performance was explored as well. The additives can improve the extreme pressure performance of base stock. TETST displays good antiwear property and EDTYP possesses excellent friction-reducing ability. Surface analysis indicated that the thermal films are exclusively composed of FeSO₄, and the tribofilms are constituted by FeS, FeS₂, and FeSO₄. The mechanism obtained from the XANES analysis fit well with the results of tribological tests.     

A procedure for obtaining complementary replicas of ultra-rapidly frozen sandwiched samples

Complementary replicas of samples prepared for electron microscopy by the freeze-fracture/etch technique are extremely valuable in the interpretation of the exposed surfaces, the nature and location of the membrane fracture plane, and as an aid in the recognition of the potential artefacts of this technique. This paper describes a procedure for the preparation of complementary replicas of thin samples sandwiched between copper foil strips and frozen ultra-rapidly in the absence of chemical pretreatments. In this procedure, the copper foil support bearing the replica is floated on the surface of a chromic acid solution, resulting in the controlled dissolution of the copper metal. The replica which remains at the surface of the chromic acid is then stabilized against fragmentation during subsequent cleaning and rinsing steps by placing a 50 mesh gold grid on top of the replica. To minimize agitation of the replica/grid, all cleaning steps are performed in a single depression plate well. The clean replica/grid is picked up from below on a thin Formvar film, dried, and then separated from the extra film. Careful placement of the gold grid on the replicas and low magnification electron micrograph montages of the complementary grids facilitate the location of complementary regions and simplify examination of complementary specimen areas at higher magnification.     

厚度效应对Pb(Zr0.53Ti0.47)O3薄膜微结构、铁电、介电性能的影响

用改进的溶胶-凝胶法在Pt(111)/Ti/SiO₂/Si(100)衬底上制备了不同厚度的高度(111)取向的Pb(Zr_0.53Ti_0.47)O₃薄膜.运用X射线衍射(XRD)和原子力显微镜(AFM)分析了薄膜的微结构,原子力显微镜表明厚度为0.3μm和0.56μm的PZT薄膜的晶粒尺寸和表面粗糙度分别为0.2～0.3μm、2～3μm和0.92nm、34nm.0.3μm和0.56μm PZT薄膜的剩余极化(Pr)和矫顽场(Ec)分别为32.2μC/²、79.9kV/cm, 27.7μC/cm²、54.4kV/cm;在频率100KHz时,薄膜的介电常数和介电损耗分别为539、0.066,821、0.029.     

Thermal Treatment Effects on Microstructure and Mechanical Properties of TiAlN Thin Films

Effects of thermal treatment on the modification of microstructure and mechanical properties of Ti_1–x Al _x N thin films (x=0.4–0.7) were investigated. It was found that the Al content plays a major role on the thermal stability and change of hardness following to heating under vacuum. The samples with the Al content x < 0.6 showed a reduction of hardness after annealing for 30 min at 1000 °C. The hardness difference between the as deposited and thermally treated samples decreased when the Al content of the films was increased. In contrast, the Al-rich samples (x > 0.6) showed a nanocomposite structure and their hardness increased after thermal treatment. Microstructural analysis by X-ray diffraction and transmission electron microscopy (TEM) revealed that the reduction of hardness in single-phase coatings is due to partial relaxation of compressive stress while the increase of hardness in the nanocomposite coatings arises from coherency stresses developed during thermal treatment.     

Nanotribology: an UHV-SFM study on thin films of AgBr(001)

We performed scanning force microscopy (SFM) in ultrahigh vacuum (UHV) on AgBr thin films which were in situ deposited on NaCl(001) substrates. The morphology of the initial growth stage and the nanotribological properties of these thin films are characterized and discussed. The lateral (frictional) forces are measured as a function of normal load. The local friction coefficients are extracted by means of the two-dimensional histogram technique. In the low load regime, friction coefficients of 0.33 ± 0.07 and <0.03 are found between probing SiO _x tip and AgBr and NaCl, respectively. The two-dimensional histogram reveals the transition from the force regime of wearless friction to the initial stage of wear on this thin film system. High-resolution SFM images of AgBr(001) are presented which reveal the atomic-scale periodicity of an unreconstructed AgBr(001) surface. The stick-slip nature of the frictional force is demonstrated.     

Thermal stability of Ti and Pt nanowires manufactured by Ga+ focused ion beam

Ti and Pt nanowires have been produced by ultra high‐vacuum molecular beam epitaxy deposition of Ti thin films and focused ion beam (FIB) deposition of Pt thin films, followed by cross‐sectional FIB sputtering to form electron‐transparent nanowires. The thermal stability of the nanowires has been investigated by in situ thermal cycling in a transmission electron microscope. Epitaxial single crystal Ti nanowires on (0001)Al₂O₃ substrates are microstructurally stable up to 550–600 °C, above which limited dislocation motion is activated shortly before the Ti‐wires oxidize. The amorphous FIB‐deposited Pt wires are stable up to 580–650 °C where partial crystallization is observed in vacuum. Faceted nanoparticles grow on the wire surface, growing into free space by surface diffusion and minimizing contact area with the underlying wire. The particles are face‐centred cubic (fcc) Pt with some dissolved Ga. Continued heating results in particle spheroidization, coalescence and growth, retaining the fcc structure.     

Influence of substrate orientation on the morphologyand orientation of LaNiO3 thin films

LaNiO₃ thin films were successfully prepared by a chemical method from citrate precursors. The LNO precursor solution was spin‐coated onto Si (100) and Si (111) substrates. To obtain epitaxial or highly oriented films, the deposited layers were slowly heated in a gradient thermal field, with a heating rate of 1° min^?1, and annealed at 700°C. The influence of different substrate orientations on the thin film morphology was investigated using atomic force microscopy and X‐ray diffraction analysis. Well‐crystallized films with grains aligned along a certain direction were obtained on both substrates. Films deposited on both substrates were very smooth, but with a different grain size and shape depending on the crystal orientation. Films deposited on Si (100) grew in the (110) direction and had elongated grains, whereas those on Si (111) grew in the (211) direction and had a quasi‐square grain shape.