Compact Thin Film Research Articles

150-GHz RF SOI-CMOS Technology in Ultrathin Regime on Organic Substrate

This letter provides an experimental demonstration of high-performance industrial MOSFETs thinned down to 5.7 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> and transferred onto a 125- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> -thick polyethylene naphthalate foil. The die stack transferred onto the organic substrate comprises the 200-nm-thick active layer and the 5.5- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> -thick interconnection multilayer stack resulting in a light, compact, and bendable thin film. We unveil that dc and RF performances are invariant even for ultimate thinning down to the buried oxide layer. Furthermore, n-MOSFET performance is improved by <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1.5}\times$</tex></formula> compared with previous work, and the first demonstration of 100-GHz p-MOSFETs on an organic substrate is presented. Unity-current-gain cutoff and maximum oscillation frequencies as high as 150/160 GHz for n-MOSFETs and 100/130 GHz for p-MOSFETs on a plastic substrate have been measured, respectively.

PECVD low temperature synthesis of carbon nanotubes coated with aluminum nitride

In this work, vertically oriented multiwalled carbon nanotubes (MWCNTs) were synthesized at 600°C by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition (ECR-PECVD) on a silicon substrate from Ni catalyst nanoparticles prepared by electrodeposition. Then CNTs were coated with aluminum nitride (AlN) by Metal Organic PECVD (MO-PECVD). The objective of this work is to obtain new nano-composite film based on AlN thin film containing oriented CNTs expected to enhance the thermal transfer compared to a single AlN layer. The final issue is the realization of thermal evacuators for microelectronic devices. Cauliflower-like structures of hexagonal AlN forming a compact thin film well coating vertically aligned CNTs were obtained and structurally characterized.

Structural and Optical Properties of ZnO Nanorods Thin Films by Solution-Growth Method

Highly c-axis-oriented ZnO nanorods thin films were obtained on silica glass substrates by a simple solution-growth technique. The most compact and vertically-aligned ZnO nanorods thin film with the thickness of ~800 nm and average hexagonal grain size of ~200 nm exhibits the average visible transmittance 85%, refractive index 1.74, and packing density 0.84. As we demonstrate here, the solution-growth technique was used to produce high-quality and dense ZnO nanorods thin films, and is an easily controlled, low-temperature, low-cost, and large-scale process for the fabrication of optical-grade thin films.

Electrodeposited nanostructured lead dioxide as a thin film electrode for a lightweight lead-acid battery

Thin films of nanostructured lead dioxide are investigated as a positive electrode material for a lightweight lead-acid battery. The films are obtained by constant current deposition from electrolytes of lead methanesulfonate in methanesulfonic acid. The films are tested in two conditions namely (a) cyclic voltammetry and (b) constant current battery cycling in sulfuric acid. The charge and discharge current density, charge density and charge efficiency are measured as a function of cycle number. The effect of deposition conditions, such as solution temperature (295 and 333 K), type of substrate and electrolyte additive (hexadecyltrimethylammonium hydroxide), on the electrochemical performance of the PbO 2 in sulfuric acid is investigated. It is found that the as-deposited lead dioxide film is compact and nanostructured β-phase structure. Following successive cycling in sulfuric acid, the compact thin film gradually transforms into a porous microstructure consisting of positive active material (PbO 2 and PbSO 4), several tens of nanometres size. The charge density, discharge density and peak discharge current density of the PbO 2 improve with cycling of the thin film electrode.

Correlation between local structure and refractive index of e-beam evaporated (HfO2–SiO2) composite thin films

In the present work we have reported the results of investigations on local structures of e-beam evaporated (HfO2–SiO2) composite thin films by synchrotron based extended x-ray absorption fine structure measurements. It has been observed that for the composite film with 10% SiO2 content, both Hf–O and Hf–Hf bond lengths are less than their values in pure HfO2 film. However the bond lengths subsequently increase to higher values as the SiO2 content in the composite films is increased further. It has also been observed that at the same composition of 10% SiO2 content, the films have smallest grain sizes (as obtained from atomic force microscopy measurements) and highest refractive index (as obtained from spectroscopic ellipsometry (SE) measurements) which suggests that the e-beam evaporated HfO2–SiO2 composite films with 10% SiO2 content leads to the most compact amorphous thin film structure.

Compact and vertically-aligned ZnO nanorod thin films by the low-temperature solution method

Highly c-axis-oriented ZnO nanorod thin films were obtained on silica glass substrates by a simple solution-growth technique. The most compact and vertically-aligned ZnO nanorod thin film with the thickness of ∼ 800 nm and average hexagonal grain size of ∼ 200 nm exhibits the average visible transmittance 85%, refractive index 1.74, packing density 0.84, and energy band gap 3.31 eV, and it was fabricated under the optimum parameters: 0.05 M, 75 °C, 6 h, multiple-stepwise, and ZnO seed layer with an average grain size of ∼ 20 nm. The photoluminescence spectrum indicates that the densest ZnO nanorod thin film possesses lots of oxygen vacancies and interstitials. As we demonstrate here, the solution-growth technique was used to produce high-quality and dense ZnO nanorod thin films, and is an easily controlled, low-temperature, low-cost, and large-scale process for the fabrication of optical-grade thin films.

High-Performance TiO2 Photoanode with an Efficient Electron Transport Network for Dye-Sensitized Solar Cells

A titanium organic sol was synthesized for the modification of conventional porous TiO2 photoanodes for dye-sensitized solar cells (DSSCs). As a result, a compact thin TiO2 film was superimposed on the porous TiO2 structure as an efficient electron transport network, covering bare conducting substrate surface (FTO) and bridging gaps between TiO2 nanoparticles, which was confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Dark current measurement suggested that the sol modified photoanode had a remarkably slower recombination rate of the photoelectrons due to the reduced bare FTO surface in comparison with the porous photoanode. The network facilitates the electron transfer in the DSSC process by removing the dead ends of electron pathways, connecting gaps along the electron pathways, and physically enlarging electron pathways, which can be demonstrated by the performance improvement of photocurrent and open-circuit potential. Consequently, the overall energy conversion efficiency of the DSSC was significantly enhanced by 28% after this simple and low-cost organic sol modification. The significant performance improvements observed from the organic sol modified DSSCs suggest that the proposed modification method is a promising alternative to the traditional TiCl4 modification method.

On the amperometric detection and electrocatalytic analysis of ascorbic acid and dopamine using a poly(acriflavine)-modified electrode

In this study, poly(acriflavine), PAF, a compact thin film, was electropolymerized on the glassy carbon (GC) electrode by cyclic voltammetry for sensing ascorbic acid (AA) and dopamine (DA). When comparing with the literatures, it was found that our GC/PAF electrode offers the second largest peak separation, 255 mV, between AA and DA at pH 7 owing to the positive nature of the PAF film. The diffusion coefficient and the intrinsic rate constant of AA were determined to be 1.84 × 10 −6 cm 2 s −1 and 0.0032 cm s −1, respectively, by the rotating disc electrode (RDE) analysis. The effect of carbon nanotube (CNT) loading was also discussed in the study. For an amperometric detection of AA in a flow injection system at 0.2 V (vs. Ag/AgCl/sat′d KCl), the sensitivity, linear range, response time, recovery time and limit of detection are 116 μA mM −1 cm −2, 3–200 μM, <2 s, 5–10 s and 1.5 μM, respectively. In the aspect of selectivity, the common interferences, DA and uric acid (UA), contribute 6.6% and 0.7% extra current, respectively for equal molar AA. For the commercial vitamin C tablet, the monitoring error caused by the GC/PAF electrode prepared in this study is only 2.6% as compared to the standard value obtained from a high-performance liquid chromatography-electrochemical (HPLC-EC) detection.

Microfluxgate sensors for high frequency and low power applications

Low cost and low power consumption are key factors to the spreading of microsystems into the everyday life tools. Fluxgate magnetometer systems still request such an improvement. This paper presents compact thin film microfluxgate sensors working in the range of tenths of kHz to tenths of MHz which exhibit improved factor of merit (FOM) in the high frequency range when the sensor size is reduced. The architecture is based on interlaced excitation and detection solenoid coils wounded around two rectangular cores made of thin film soft magnetic sputtered NiFe permalloy material. Measurement axis and magnetic hard axis are along core length. These thin film sensors also proved to be working in a wide range of excitation currents since deep saturation is not requested thanks to a highly nonlinear hysteresis loop. Excitation currents as low as 6mA lead to still linear output response. Devices with monolayer cores were measured up to 20MHz. Laminated cores were measured up to 73MHz. Frequency response higher than 100MHz is achieved when magnetostatic coupling occurs between laminated layers. The power consumption can be monitored at system level to adjust the sensor sensitivity within a range of 0.5 to more than 220V/T.

Buildup of gold nanoparticle multilayer thin films based on the covalent-bonding interaction between boronic acids and polyols

A novel method for the fabrication of gold nanoparticle multilayer films based on the covalent-bonding interaction between boronic acid and polyols, poly(vinyl alcohol) (PVA), was developed. The multilayer buildup was monitored by UV–vis absorbance spectroscopy, which showed a linear increase of the film absorbance with the number of adsorbed Au layers and indicated the stepwise and uniform assembling process. The atomic force microscopy (AFM) image showed that a compact gold multilayer thin film was successfully assembled. The residual boronic acid group on the surface of thin film could incorporate glycosylated-protein horseradish peroxidase (HRP), and good catalytic activity for H 2O 2 could be observed.

The compact microcrystalline Si thin film with structure uniformity in the growth direction by hydrogen dilution profile

The hydrogen dilution profiling (HDP) technique has been developed to improve the quality and the crystalline uniformity in the growth direction of μc-Si:H thin films prepared by hot-wire chemical-vapor deposition. The high H dilution in the initial growth stage reduces the amorphous transition layer from 30–50 to less than 10 nm. The uniformity of crystalline content Xc in the growth direction was much improved by the proper design of hydrogen dilution profiling which effectively controls the nonuniform transition region of Xc from 300 to less than 30 nm. Furthermore, the HDP approach restrains the formation of microvoids in μc-Si:H thin films with a high Xc and enhances the compactness of the film. As a result the stability of μc-Si:H thin films by HDP against the oxygen diffusion, as well as the electrical property, is much improved.

Glancing Angle Deposition Thin Film Microstructures for Microfluidic Applications

Microfluidic channels (A) were fabricated by a new GLAD method with thin film porosity engineering capabilities. Smooth areas of a substrate result in fairly compact thin film morphology (C) while areas of the same substrate pre-patterned with a periodic array of seeds (B) are quite porous and permit liquid flow.

Remote electro-precipitation of transparent ZnO on nano-porous alumina template

Zinc oxide (ZnO) thin film was deposited onto non-conducting alumina template by remote electrochemical and precipitation method. Chronoamperometry (i.e., constant potential mode) of −0.75 V (versus Ag/AgCl) was applied to deposit compact ZnO thin film onto the honeycomb shaped pores of a nano-porous alumina membrane. Analyzing morphological observations by SEM, we observed three distinct regions: (i) conducting platinum substrate; (ii) non-conducting alumina interlayer; (iii) thin film onto alumina template. XRD structural analysis of deposited materials onto alumina template and EDX analysis of alumina layer clearly indicated the formation of ZnO thin film was formed onto non-conducting alumina template not inside of alumina template. This remote-deposited ZnO showed more compact ZnO-hexagonal structure and a little bit higher transmittance than conventionally prepared ZnO onto ITO glass. Experimental observations were further discussed via the understanding of the mechanistic origin of ZnO formation onto alumina template.

Effect of texture and annealing treatments in SnO 2 and Pd/SnO 2 gas sensor materials

The chemical reactivity of a series of SnO 2 materials with different textures has been studied by XPS. A nanocrystalline SnO 2 (n-SnO 2) powder, a powder sample with a crystal size of several microns and a very compact thin film have been chosen for this comparative study. It is found that the degree of reduction upon heating in H 2 (i.e., percentage of Sn 2+/Sn 0) decreases with the degree of compaction of the samples. Thus, while in an n-SnO 2 powder a 29% reduction is obtained after heating in H 2 at 773 K, a negligible reduction was found for the compact SnO 2 thin film prepared by ion beam-induced CVD (IBICVD). This latter material has been chosen as a suitable substrate to characterize the state and function of palladium in Pd/SnO 2 sensors. Palladium was added onto the SnO 2 surface in the form of a PdCl 2 salt. Then, the sample was subjected to different thermal activation processes. Conductivity measurements at different temperatures and under several pressures of H 2 and O 2 have been carried out with the samples. Texture and previous treatments have been found to be critical factors determining the gas sensing properties of SnO 2 and Pd/SnO 2 samples. A correlation is intended between the characteristics of the Pd 3d XPS signal after the different thermal treatments and the conductance response of the Pd/SnO 2 system towards the exposure to H 2/O 2 cycles.

Pd–Ni thin films grown on porous Al2O3 substrates by metalorganic chemical vapor deposition for hydrogen sensing

Pd–Ni thin films were grown on porous substrates by metalorganic chemical vapor deposition (MOCVD) using the Pd- and Ni-acetylacetonate mixed precursor. Porous α-Al2O3 disks with and without γ-Al2O3 top layer deposited by a sol-gel process were employed as substrates. The composition of the films was very close to the Pd/Ni ratio in the mixed precursor as shown by X-ray photoelectron spectroscopy (XPS) analysis. The microstructure and surface morphology of the Pd–Ni thin film was determined by using scanning electron microscope (SEM) and atomic force microscope (AFM). The porous substrates have a remarkable effect on the film morphology, which contributes to different hydrogen sensing properties. The deposited film on a porous α-Al2O3 substrate was porous and discontinuous due to the large pores of the substrate used, and the sensitivity to hydrogen is significantly larger than that of Pd–Ni thin film sensors reported in the literature. On the contrary, the deposited film on porous γ-Al2O3 surface with bright metallic mirror provided a more uniform and compact thin film, and the sensitivity to hydrogen is much lower than that of the film on porous α-Al2O3 and blisters are easily formed under hydrogen atmosphere.

A linear array thin film position sensitive detector for 3D measurements

A novel compact linear thin film position sensitive detector with 128 elements, based on p-i-n a-Si:H devices was developed. The proper incorporation of this sensor into an optical inspection camera makes possible the acquisition of three dimension information of an object, using laser triangulation methods. The main advantages of this system, when compared with the conventional charge-coupled devices, are the low complexity of hardware and software used and that the information can be continuously processed (analogue detection).

Alkene oxidation over the Mo–Bi mixed oxides/Au | yttria-stabilized zirconia | Ag system

Oxidation of propene and but-1-ene has been carried out in an MoO3–Bi2O3/Au | yttria-stabilized zirconia (YSZ)| Ag electrochemical reactor at 723 K and compared with the result obtained by means of a mixed-gas flow reaction over the MoO3–Bi2O3 catalyst. The MoO3–Bi2O3 catalyst was prepared from MoO3, three phases of bismuth molybdate [Bi2Mo3O12(α), Bi2Mo2O9(β), Bi2MoO6(γ)] and Bi2O3 and each catalyst was successfully deposited by vacuum evaporation as a compact thin film on the Au anode. For propene oxidation, MoO3 showed the highest activity among the catalysts used on the Au anode and its activity was up to 600 times higher than that obtained with the same catalyst using a mixed-gas flow reaction. These results suggest that oxygen species bound to molybdenum metal possess a definite role for both α-H abstraction from propene and oxygen insertion into the allylic intermediate under a sufficient oxygen supply. On the other hand, oxygen can permeate through a Bi2O3 film, suggesting that the bismuth species is effective for O2 incorporation into the catalyst and also for transportation of oxide ions through the catalyst bulk. Each phenomenon, i.e. the insertion of lattice oxide ions into the allylic intermediate and O2 incorporation into the lattice was separately observed. The electrochemical-reactor system showed some advantages for propene oxidation, e.g. high selectivity to arylaldehyde under high reaction temperatures and higher activity, compared with the mixed-gas flow reaction. In but-1-ene oxidation the main product was buta-1,3-diene by oxidative dehydrogenation and Bi2Mo2O9(β) showed the highest activity. The critical effect of molybdenum species was not observed in this reaction but high activity was still obtained over the molybdenum-rich catalysts.

Combined scanning tunneling and force microscopy

A combined scanning tunneling and force microscope (STM/FM) was built which allows for the simultaneous measurement of forces and force gradients along STM constant current contours. Measuring Au(111) surfaces with this combined STM/FM, very low tip–sample interaction forces and variations of the local stiffness (force gradient) in the vicinity of single adsorbates and domain boundaries of the Au(111) (√3×23) surface reconstruction were found. On Au(111) substrates covered by a compact thin organic film the interaction force is higher, indicating repulsive contact between tip and sample. An elastic theory for the deconvolution of real topography from local electronic and sample deformation effects on STM constant current contours of soft samples was developed.

AES and SIMS investigations of the oxide films on Fe-40Cr-Ru alloys

Auger and SIMS depth profiling have been used to investigate the effect of ruthenium addition on the oxidation behaviour of the Fe-40Cr-Ru alloys oxidized in air at 500 °C. Auger results revealed that the oxide films formed on the Fe-40Cr-Ru alloys consisted of a thin iron oxide external layer and a chromium-rich internal layer. Ruthenium was not found in these oxide layers. Secondary ion mass spectrometry measurements also indicated a thin Fe+-rich film as an outer layer with a predominantly chromium oxide in the internal layer of the film. Furthermore, ruthenium was incorporated in the entire oxide film and promoted the formation of a thin compact film.

高純度鉄の腐食特性

The corrosion resistance of iron in acid and neutral chloride solutions has been investigated as a function of the purity of iron. Five kinds of iron having residual resistivity ratios, RRRH,4.2K, of 80, 150, 800, 1500 and 6000 were used as specimens. The former three with RRRH,4.2K 80, 150 and 800 were commercially available pure iron and the latter two with RRRH,4.2K 1500 and 6000 were high purity iron produced by a new method combining anion exchange and zone-refining processes.In deaerated 0.5 kmol·m−3 H2SO4, the corrosion rate of iron decreased sharply with increasing purity; the corrosion rate of iron with RRRH,4.2K 6000 showed only 2% of that of the one with RRRH,4.2K 80. From the examination of cathodic polarization curves in the solution, it was confirmed that the increased hydrogen overpotential of high purity iron resulted in the decrease of corrosion rate.Concerning the pitting corrosion in aerated 0.1 kmol·m−3 NaCl, the corrosion rate decreased slightly with increasing purity. The pitting potential and the induction time for pitting were, however, found to depend strongly on the purity of iron; the values of them measured in a pH 8.45 boric-borate buffer solution containing 0.01 kmol·m−3 NaCl increased sharply with increasing purity. This increased resistance against the initiation of pitting can be ascribed to the improved nature of passive films on high purity iron. The formation of thin compact films with low carrier concentration has been confirmed in situ by ellipsometric and impedance measurements on high purity iron in a pH 8.45 boric-borate buffer solution.