Nano-thick Films Research Articles

Optical, Dielectric and Optoelectronic Properties of Spray Deposited Cu-doped Fe2O3 Thin Films

Copper-doped hematite thin films were prepared by spray pyrolysis technique using a mixture of ethanol and distilled water precursors. Visual observations showed that aqua precursor produced films of less integrity compared with ethanol that produced thin, uniform and transparent yellowish-brown films that adhered well to the substrate. Composition and thickness measurements determined by RBS revealed that ethanol precursor produced thinner films of 94.45 and 51.77 nm while aqua precursor produced films of 1,370 and 1,120 nm for undoped and Cu-doped Fe2O3 respectively. This is an indication that ethanol solutions produced nano-thick films of high integrity. The composition revealed that only the Cu-doped Fe2O3 deposited by ethanol solution gave composition close to stoichiometric Fe2O3 while the others gave non-stoichiometric Fe(OH)3 . Optical characterization carried out using UV-visible spectrophotometer in transmittance mode indicated that the film thickness was directly proportional to the number of passes which is inversely proportional to the transmittance. Three bandgap determination methods namely; Tauc, Absorption Fitting Spectrum (AFS) and Davis-Mott were employed with the result that Tauc and AFS gave close direct and indirect bandgap energies (Eg) of 3.44 and 1.98 for AFS and 3.43 and 2.32 eV for Tauc respectively. The Urbach tail energy determined was 1,100 meV which is an indication of a broad onset of absorption. The steepness parameter (?) was found to be 7.83 while the electron-phonon (Eph ) coupling energy was found to be 0.85 eV. It was also observed that the refractive index (n) was about 15 times greater than the extinction coefficient (k). In the study of the dispersion parameters using single oscillator and Sellmier models, the values of the single oscillator energy (Eosc ), dispersion energy (Ed), zero frequency dielectric constant, zero frequency refractive index, the average oscillator strength (So), the average oscillator parameter and the dispersion parameters were determined. All the values of the parameters estimated are of the same order of magnitude with other semiconducting materials. The study showed that Cu-doped Fe2O3 could be employed as dielectric material as well as in optoelectronic devices.

Evaporation Mitigation Assessment by Self-assembled Nano-thickness Films in Shallow Fresh Water Lake Using Fixed and Semi-Floating Pans

Evaporation Mitigation Assessment by Self-assembled Nano-thickness Films in Shallow Fresh Water Lake Using Fixed and Semi-Floating Pans

Mechanical Characterization of Polymeric Thin Films Using Nano Cutting Method

In the ultra-precision industry, physical and chemical coatings are used to provide functional properties to the surface. Especially, it is very important to examine the mechanical durability of polymer thin films with super hydrophobic properties. The mechanical durability of the thin film includes adhesion force and shear strength, and the latter can be measured with precise cutting. A sharp blade capable of changing cutting direction is used for cutting nano-thick films. Then, nano cutting method is used to calculate the shear strength by measuring the resistant forces when the blade cuts thin films simultaneously in the horizontal and vertical directions (slanted cutting). In this study, we prepared two super-hydrophobic fluoropolymers, p(PFDMA) (1H, 1H, 2H, 2H-perfluorodecyl methacrylate) thin film and p(V4D4-PFDMA-co-DVB) thin film, using initiated chemical vapor deposition method. Especially, p(V4D4-PFDMA-co-DVB) thin film was obtained by continuous deposition with V4D4 (1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) and DVB (C6H4(CH=CH2)2, divinylbenzene) in order to improve its durability, and the abrasion test was performed to quantitatively check the durability. In order to qualitatively assess the durability, the thin film was cut with a customized precision-cutting tool, and the shear strength and adhesion force were analyzed. As a result, it was confirmed that the mechanical durability of p(V4D4-PFDMA-co-DVB) thin film has dramatically improved compared to p(PFDMA) thin film. In addition, the nano cutting theory was successfully verified to evaluate the mechanical properties of thin films.

Surface morphology and electrical transport properties of Aberchrome 670 ( (E-3(admantan-2-ylidene) -4-[1-(2,5-dimethyl-3-furyl) ethyldene] dihydro-2,5-furandione)) nano thickness films

In this paper, surface morphology and electrical properties of Aberchrome 670 , [(E-3(admantan-2-ylidene)-4-[1-(2,5-dimethyl-3-furyl) ethyldene] dihydro -2,5-furandione)], thin films with nano thickness, have been studied, for the first time, to provide one with knowledge concerning microscopic features, for electrical applications of organic photochromic compounds. The atomic force microscope (AFM) has been used to convene a general spectacle about the surface. The cyclic-voltammetric measurement has been inserted to determine the electrochemical gap. The thermal effect on the electrical resistivity, the thermoelectric power and Seebeck coefficient have been measured from 298 to 373 K. The influence of the frequency on some dielectric characteristics; such as the capacitance, the temperature capacitance coefficient (T.C.C), the real part of the complex dielectric permittivity (), the dissipation factor (tan (δ)) has been studied in the frequency zone (50 -5 MHz) and temperature range (∼298–373 K) at different steady temperatures.

Comparative measurements of local and nonlocal spin Seebeck effect in YIG/Pt nano-thick films

Abstract We systematically compared the local and nonlocal spin Seebeck effect (SSE) in YIG/Pt nano-thick films. Their dependences on heating current, magnetic field and temperature were studied. Both the local and nonlocal SSE are quadratically related to heating current while their dependences on the magnetic field are distinguishing. The local SSE is seldomly affected but the nonlocal one is obviously suppressed by high magnetic field. Besides, local SSE gradually enhances to maximum around 150 K and then quickly decreases. However, nonlocal SSE monotonously grows up from 50 to 300 K. The transport properties of the associated spin current in local and nonlocal SSE are found to be different which is possibly due to that the local signal is directly related to the temperature difference at the interface whereas the nonlocal one is mainly driven by the spin chemical potential.

Fabrication and characterization of CdS doped ZnO nano thick films

In the present work, microstructural and optical properties of Cadmium Sulfide (CdS) doped Zinc Oxide (ZnO) thick film is investigated. Two samples undoped ZnO and 2 wt % CdS-doped ZnO thick film have been fabricated on the glass substrate. The fabricated film is characterized by X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM). X-ray diffraction patterns showed that crystallite size decreasing with CdS doping and it is 45 nm and 38 nm for ZnO and CdS-doped ZnO thick film. The variation on the surface morphology was observed using AFM measurement. The AFM results indicate that grain size and roughness parameter decreases, but microstrain increases with CdS content. The UV–Vis absorption spectra of the ZnO and ZnO-CdS showed that the optical band-gap decreased from 3.18eV to 2.10eV with 2 wt% CdS doping concentration. The present study demonstrates that fabricated films have polycrystalline structures and peaks matching the hexagonal ZnO structure.

BEOL Dielectric Processing for Cu-Low k Nano Interconnect- Impact of Plasma CVD Initial Transient Phenomena (ITP)

The Initial Transient Phenomena (ITP) during plasma CVD, its impact in nano thick film fabrication and methods to mitigate any negative impact from this phenomenon are presented in this paper. Plasma deposited dielectrics such as SiCOH, SiNx, SiCNx are regularly used for Cu low-k interconnect fabrication. For lightly porous low-k SiCOH films deposited with organosilicon and oxygen precursors, an initial C-Rich SiCOH is typically deposited at the interface due to ITP and the intrinsic plasma deposition chemistry. This carbon rich interface will weaken the film’s adhesion to the underlying surface and degrade the electrical properties of the nano-thick SiCOH dielectric. For SiCNx or SiNx dielectric films, local and global ITP charging effects on blanket and patterned surfaces have significant impacts on film’s quality and thickness control. Various novel process modifications were developed to mitigate this and to improve the plasma CVD dielectric film.

Initial Transient Phenomena Impact on Plasma CVD of Ultrathin Silicon Nitride and Silicon Carbon Nitride Dielectrics for Nano Devices Cu-Low k Interconnects

The initial transient (ITS) phenomena in plasma enhanced Chemical Vapor Deposition (PECVD) process was identified in early 1980’s (1). This ITS phenomenon has impact on the bonding structure and composition of plasma deposited silicon nitride (1) and amorphous silicon (2) films at the initial film-substrate interface. When the deposited film is in micron thickness, the ITS impact is generally smaller. The shrinking of semiconductor devices and the corresponding push to increase device density is continuing in the quest for improved performance of integrated circuits. Nano scale thickness low temperature plasma CVD dielectric films such as silicon nitride and silicon carbon nitride used as cap materials (3) for Cu interconnects that are expected to reach to sub-10 nm dimension next few years. The compositional variation in PECVD films at the interface by ITS which had a relatively small impact in past semiconductor technologies is becoming a significant factor in film’s properties as we scale film thickness down to sub-10nm. In this paper, we will present in detail the impact of the initial transient plasma in CVD process on the ultrathin nano thick cap and-low k dielectric films that are being used for advanced device interconnect fabrication, We will show that we can modify the current standard PECVD process to alleviate the impact of ITS phenomena. Some ITS impact on nano thick film are: a) PECVD silicon nitride / silicon carbon nitride dielectric cap films are normally deposited with a mixture of silane/ammonia or other carbosilane/ammonia precursors. The initial breakdown of silane is strongly affected by the plasma conditions and the dissociation thermodynamic of the precursors. Deposition rates can be different on Cu versus dielectric surfaces due differences in charging effects (see Figure 1). Additionally, the silane molecule is relatively unstable and more reactive as compared to ammonia, and typically dissociate rapidly first to form more conformal SiHx deposition radicals before the plasma reaches a steady state. Subsequently, PECVD with SiH4/NH3 precursors will normally produce a Si-rich silicon nitride composition at the interface. Silicon carbon nitride films can be deposited from more stable carbosilane precursors. In this case, the thickness of the Si-rich interface zone can be reduced, and a C-rich film surface may be deposited under specific deposition condition. This modulation may be exploited to control electrical (k, breakdown/leakage) and adhesion properties of the film for Cu low k interconnect structures. For a very thin dielectric cap deposited on a patterned structure of Cu and ultra-low k dielectric, the film thickness deposited on Cu versus the dielectric surface will be slightly different due to the differential local plasma charging effect during initial transient deposition period as shown in fig 1. This deposition rate difference will impact the film’s barrier and electrical properties, gap fill performance and subsequent in Cu-low k fabrication. In this case, plasma ITS charging is the principle mechanism that cause differences in film’s thickness. b) For typical PECVD SiN deposition process, the initial dissociation of SiH4 and/or NH3 will create reactive species that subsequently etch the deposited ultra-low k pSiCOH dielectric surface. These reactive species can produce substantial damage to pSiCOH, increase dielectric constant and subsequently poor reliability in final electronic devices. This damage can be reduced significantly by using an initially low rf plasma power and then increasing to a higher rf plasma power for the remainder of the deposition (4). ITS negative impact to devices and mitigation method will be discussed. c) For ultrathin cap films for Cu interconnects, such as SiN, variations in film composition at the interface will cause significant variation in electrical properties and conformality. To mitigate the ITS effect, a cyclic, multi-step deposition process utilizing plasma surface treatment was developed. A multilayers film with better conformality and consistent film’s properties was achieved. Using this novel cyclic process, high quality dielectrics SiN and SiNO at sub-10 nm thickness can be deposited consistently and reproducibly for Cu-low k interconnect fabrication as showed in Figure 2. In summary, the ITS phenomena on plasma CVD, its impact in nano thick film fabrication and methods to mitigate the ITS’s negative impact will be presented in the paper.

Microstructures, optical and electrical properties of TiO2 thin films prepared by unconventional sol–gel route

Band gap lowering in TiO2 is usually done by adding impurity to it. In this paper a new approach is adopted to make TiO2 thin films by unconventional sol–gel method starting with TiO2 powder reagent. The prepared gel is deposited on the microscopic glass slide by doctor blade technique. The prepared films were then subjected to X-ray diffraction for structural and microstructural analysis. Different optical parameters like, thickness, refractive index, extinction coefficient, transmittance and absorbance etc. are calculated and finally band gap of the samples are estimated and are presented in this work. Both the refractive indices and band gap are found to be lower than that reported earlier. Scanning electron microscope image shows dense and uniformly distributed TiO2 particles. The quality and novelty of this paper is that, the micro size nano thick film is prepared from powder reagent unlike other published papers and novelty lies in its very low band gap as direct transition is more favorable for TiO2 nanoparticles in anatase phase.

Nanothickness films, nanostructured films, and nanocrystals of barium titanate obtained directly by a newly developed sol–gel synthesis pathway

This work aims to develop a chemically modified sol–gel synthesis pathway for obtaining various barium titanate nanostructures. The method is able to prepare different BaTiO3 nanostructures such as highly stable nanoparticle embedded colloids, highly transparent amorphous nanolayers, nanocrystalline BaTiO3 powders and ultrathin BaTiO3 nanostructured films directly from a precursor solution. All the products have been prepared at a lower temperature and in a more cost-effective way in contrast to other established sol–gel methods. The results show that the optical transparency of the thin films has been significantly improved in contrast to the similar researches. The deposited thin film is highly transparent with an average transmission of 87 % in the wavelength range from 400 to 1,200 nm, which this transparency is higher than the reported values in the similar researches in those, the average transmissions in the range of 70–75 % have been reported. From the study of the relationships between structure and properties of the products, it is found that the optical transparency enhancement in the thin films is due to the size of the particles within the precursor solution, which is in the range of a few nanometers. The above-mentioned advantages have been reached thanks to the applied modifications, which result in the drastic downsizing the particles within the precursor solution.

Nanofilms of adsorbed water in clay: Mechanism of formation and properties

The process of adsorption of water molecules by silicate surfaces of clay minerals is considered. The process leads to the formation of nano-thickness films of adsorbed water. An epitaxial mechanism of nanofilm formation is considered, consisting in the growth of structured hydrate layers under the effect of oxygen and hydroxyl surfaces of clay minerals. The difference between the sizes of hexagonal cells of the solid surface and the forming water film deforms hydrogen bonds and produces inner stress in both the film structure and the mineral lattice. The latter is reflected in the changing size of montmorillonite cell along the b-axis. The thickness of the newly formed adsorption water layer is shown to be controlled by the degree of hydrogen bond deformation, the stress developed inside the nanofilm, the cell size, and the rigidity (strength) of the mineral structure. The deformation of hydrogen bonds and water nanofilm structure determines its specific properties, i.e., wedging pressure, high viscosity, low temperatures of water freezing, dielectric conductivity, etc.

OS1301 ナノメートル厚金属薄膜の破壊じん性に及ぼす膜厚効果

OS1301 ナノメートル厚金属薄膜の破壊じん性に及ぼす膜厚効果

Evaluation of Interfacial Strength of Copper Thin Film on Printed Circuit Board with Micro Cutting System

The purpose of this paper is to develop the evaluation method of interfacial strengths with a micro cutting system. The interfacial strength of thin films is crucial for the reliability assessment of electronics packages and MEMS devices. There have been a lot of experimental and theoretical studies about the measurement of interfacial strengths. However, it is still under developing stages, because it is quite difficult to measure it quantitatively for micro- and nano-thickness films. Recently, SAICAS(Surface and Interfacial Cutting Analysis System) has been developed and used for the evaluation of the mechanical properties in micro- and nano-thickness films. In this paper, we developed the theoretical model of SAICAS micro cutting tests and proposed the evaluation method of interfacial strength for thin films systems. The proposed method was applied to copper thin films on printed circuit boards and compared with 90° peel tests. The results show that the proposed method can exclude the plastic and friction dissipation energies during the SAICAS tests and quantitatively evaluate the interfacial strength.

Crystallized Nano-thick ZnO Films with Low Temperature ALD Process

Crystallized Nano-thick ZnO Films with Low Temperature ALD Process

PS50 切削原理を利用した界面強度評価(フェロー賞対象ポスターセッション)

The purpose of this paper is to develop the evaluation method of interfacial strengths with a micro cutting system. The interfacial strength of thin films is crucial for the reliability assessment of electronics packages and MEMS devices. There have been a lot of experimental and theoretical studies about the measurement of interfacial strengths. However, it is still under developing stages, because it is quite difficult to measure it quantitatively for micro- and nano-thickness films. Recently, SAICAS(Surface and Interfacial Cutting Analysis System) has been developed and used for the evaluation of the mechanical properties in micro- and nano-thickness films. In this paper, we carried out the numerical simulation of SAICAS micro cutting tests by Multibody dynamics with HyperWorks and analyzed the behavior of peeled film.

Food for thought … on alternative methods for nanoparticle safety testing

Nano is a big thing in toxicology. Articles, journals, and conferences are mushrooming, paralleling the rise of nanotechnologies but also showing the hunger of toxicology for new objects to study. Perhaps it would be better to focus on new approaches first? Nanomedicine promises new solutions for old problems, but what about the old problems of toxicology? It is a fallacy to assume that one can gain beneficial effects in the human organism without unwanted collateral effects. First, any biologically active agent perturbs physiology, hopefully as a corrective for the patient but at least requiring compensatory reactions of the healthy. Second, few agents are specific enough to have only one effect, but it is rare that we want all the effects and in the given mix of strengths. third, many agents show excess toxicity – even desired effects often become negative if excessively stimulated. this increase in negative effects is directly linked to more sensitive subpopulations (children, elderly, the diseased, those with genetic polymorphisms, etc.). thus, the promise of nanoparticles (NP) may be paid for in possible side-effects, i.e., toxicities (Garnett et al., 2006). For most manufactured NP, toxicity data are unavailable, with some exceptions for carbon black, titanium dioxide, iron oxides, and amorphous silica (Di Giacchino et al., 2009). So far nanoparticles and other nanomaterials (I will use the abbreviation NP for both but primarily thinking of particles or fibers and not e.g. nano-thick films) are, for the most part, treated by regulatory toxicology as chemicals (see last issue of this series, Hartung, 2010b). The most common definitions for NP include materials with dimensions from 1 nm (size of a sugar molecule) to 100 nm (size of a virus). Regulatory frameworks are on the way, opening up possibilities for alternative approaches (Sauer, 2009). Whether the differences between NP and their parent compounds are actually small or big problems, remains to be seen. But to quote Albert einstein: “Anyone who doesn’t take truth seriously in small matters cannot be trusted in large ones either.” When discussing alternative methods for nanoparticle toxicology, we might first look at some phrase permutations – leaving out one word in each iteration: – Alternative methods for toxicology – Methods for nanoparticle toxicology – Alternative nanoparticle toxicology – Alternative nano-methods Consideration 1: Alternative or advanced methods for toxicology?

F-3 2段結像型エリプソメトリー顕微鏡による液体ナノ薄膜の動的可視化(マイクロナノ理工学)

F-3 2段結像型エリプソメトリー顕微鏡による液体ナノ薄膜の動的可視化(マイクロナノ理工学)

Atomic Layer Deposition of UV‐Absorbing ZnO Films on SiO2 and TiO2 Nanoparticles Using a Fluidized Bed Reactor

AbstractAtomic layer deposition (ALD) was used to apply conformal, nanothick ZnO coatings on particle substrates using a fluidized bed reactor. Diethylzinc (DEZ) and water were used as precursors at 177 °C. Observed growth rates were ca. 2.0 Å/cycle on primary particles as verified by HRTEM. ICP‐AES and XPS were used to quantify Zn:substrate ratios. Layers of 6, 18, and 30 nm were deposited on 550 nm SiO2 spheres for UV blocking cosmetics particles. TiO2 nanoparticles were coated in the second part of this work by ZnO shells of 2, 5, and 10 nm thickness as novel inorganic sunscreen particles. The specific surface area of powders changed appropriately after nanothick film deposition using optimized conditions, signifying that high SA particles can be functionalized without agglomeration. The ZnO layers were polycrystalline as deposited and narrowing of the FWHM occurred upon annealing. Annealing the ZnO‐TiO2 nanocomposite powder to 600 °C caused the formation of zinc titanate (Zn2TiO4) in both oxygen‐rich and oxygen‐deficient environments. The non‐ideal surface behavior of the DEZ precursor became problematic for the much longer times required for high surface area nanoparticle processing and results in Zn‐rich films at this growth temperature. In situ mass spectrometry provides process control capability to functionalize bulk quantities of nano‐ and ultrafine particles without significant precursor waste or process overruns. ZnO overlayers can be efficiently deposited on the surfaces of primary particles using ALD processing in a scalable fluidized bed reactor.

Thin-film lubrication nano-rheology via molecular dynamics

There are many curious phenomena when very thin lubricant films interact with sliding surfaces. It is difficult to do experiments on these nano-thickness films, and here we describe the use of non-equilibrium molecular dynamics (MD) to investigate friction in alkane lubricant layers. The pronounced increase of viscosity in layers of thickness seven molecules and less enables an increased load capacity to be sustained in such films. We also demonstrate the existence of a newly-discovered low-friction regime.

Properties of nickel-cobalt composite silicides by thermal annealing of Ni1−xCox (x=0.2, 0.5, and 0.8) alloy thin films on silicon and polysilicon substrates

10 nm-Ni1−xCox (x=0.2, 0.5, and 0.8)/p-Si(100)(or poly crystalline Si) was thermally annealed using rapid thermal annealing for 40 s at 600–1100°C. The annealed film structures developed into NiCoSix, and the resulting changes in sheet resistance, microstructure, and composition were investigated using a four-point probe, a scanning electron microscope, a field ion beam, an X-ray diffractometer, and an Auger electron spectroscope. The final thickness of NiCoSix formed on single-crystal silicon was approximately 12.64nm, and it maintained its sheet resistance below 20 Ω/sq. during the silicidation annealing at 1100°C. The NiCoSix formed on polysilicon had a thickness of 35.04nm, and its low resistance was maintained up to 900°C. Additional annealing of silicides at the given RTA temperature for 30 min resulted in a drastic increase in sheet resistance. We identified Ni3Si2 and a NiSi phase at 700°C and 1000°C for single-crystal silicon substrates. Moreover, Ni3Si2, NiSi, and CoSi2 phases were stable at 700°C, and then NiSi2 and Ni3Si2 became stable for polycrystalline silicon substrates at 1000°C. When the amount of Co was 80%, only a Ni3Si2 phase was confirmed at 700°C and 1000°C in both the single and polycrystalline substrates. With less Co (Co=0.2, 0.5), Ni3Si2, NiSi, and CoSi2 phases were observed at 700, and Ni3Si2 and NiSi2 phases were observed at 1000°C. Cobalt also improved thermal stability of the silicides formed on the polysilicon gate, but this enhancement was lessened due to the silicon mixing during high temperature diffusion. In conclusion, the proposed nickel cobalt composite silicides formed from the nano-thick alloy films may be superior to conventional nickel monosilicides due to improved thermal stability.