Deposition Of Functional Thin Films Research Articles

Effects of process parameters on optical characteristics of diamond-like carbon thin films deposited using high-power impulse magnetron sputtering

High-power impulse magnetron sputtering (HiPIMS) is a physical vapor deposition technique, developed specifically for the low-temperature deposition of functional thin films. In this study, a graphite target was used for the deposition of diamond-like carbon (DLC) thin films of high optical transmittance on a quartz glass substrate at 25 °C – 30 °C using HiPIMS in unipolar and bipolar modes. Experiments were conducted to determine the influence of DC input power, deposition time, and bias voltage with a fixed duty cycle on the optical characteristics of the resulting amorphous DLC thin films. During deposition, the current-voltage characteristics of discharge with a graphite target were recorded. The optical characteristics were assessed using a UV/visible light-absorption detector and the structure of the DLC thin films was confirmed by Raman spectroscopy. DLC thin films produced in unipolar mode with deposition time of 1 min presented the highest best transmittance of 86%.

Analysis of mist flow in functional thin film deposition system "KAGUYA" and optimization of flow path and deposition conditions

Analysis of mist flow in functional thin film deposition system "KAGUYA" and optimization of flow path and deposition conditions

Thin film deposition based on microacoustic sol atomization (MASA)

In this work, we demonstrate an innovative method for the deposition of functional thin films, based on microacoustic sol atomization (MASA) and subsequent gel condensation. This method offers several advantages over existing sol–gel deposition methods (e.g., ink-jet printing or dip coating), including a narrow droplet-size distribution with droplets in the low micrometer range, a miniaturizable aerosol source and the principle usability in roll-to-roll processes. The technique can be divided into three subsequent steps: In a first step, high-frequency surface acoustic waves atomize precursor solutions (sols) into an ultra-fine aerosol. In a second step, the aerosol condensates on the substrate surface, forming a gel, which in a third step can be pyrolyzed into a crystalline thin film. The new technique is demonstrated for the deposition of La2Zr2O7 buffer layers on biaxially textured Ni–5 %W tapes. Aerosols with median droplet diameters of 4 and 7.5 µm were produced from lanthanum/zirconium precursor solutions based on propionic acid or water, respectively. A continuous aerosol production was maintained for several minutes, allowing a droplet condensation on an area of about 1 cm × 5 cm. X-ray diffraction studies of the crystallized La2Zr2O7 films with a thickness of about 100 nm show a high crystalline quality with a strong (001) orientation. Additionally, our results indicate a significant influence of the fluid chemistry regarding the aerosol formation, as well as the droplet condensation and the thin film formation process, when the impinging droplets contain residual solvent. The deposition of functional thin films by microacoustic sol atomization (MASA) and subsequent condensation is demonstrated here for La2Zr2O7 buffer layers on biaxially textured Ni–5 %W tapes. Aerosols with median droplet diameters of 4 and 7.5 µm were produced via interaction of lanthanum/zirconium precursor solutions based on propionic acid or water, respectively, with high-power surface acoustic waves. A continuous aerosol production was maintained for several minutes, allowing a droplet condensation on an area of about 1 cm × 5 cm. X-ray diffraction studies of the crystallized La2Zr2O7 films with a thickness of about 100 nm show a high crystalline quality with a strong (001)-orientation.

In SituChemical Oxidation of UltrasmallMoOxNanoparticles in Suspensions

Nanoparticle suspensions represent a promising route toward low cost, large area solution deposition of functional thin films for applications in energy conversion, flexible electronics, and sensors. However, parameters such size, stoichiometry, and electronic properties must be controlled to achieve best results for the target application. In this report, we demonstrate that such control can be achieved viain situchemical oxidation ofMoOxnanoparticles in suspensions. Starting from a microwave-synthesized suspension of ultrasmall (d~2 nm)MoOxnanoparticles in n-butanol, we added H2O2at room temperature to chemically oxidize the nanoparticles. We systematically varied H2O2concentration and reaction time and found that they significantly affected oxidation state and work function ofMoOxnanoparticle films. In particular, we achieved a continuous tuning ofMoOxwork function from 4.4 to 5.0 eV, corresponding to oxidation of as-synthesizedMoOxnanoparticle (20% Mo6+) to essentially pure MoO3. This was achieved without significantly modifying nanoparticle size or stability. Such precise control ofMoOxstoichiometry and work function is critical for the optimization ofMoOxnanoparticles for applications in organic optoelectronics. Moreover, the simplicity of the chemical oxidation procedure should be applicable for the development of other transition oxide nanomaterials with tunable composition and properties.

Conformal Polymeric Thin Films by Low-Temperature Rapid Initiated Chemical Vapor Deposition (iCVD) Using tert-Butyl Peroxybenzoate as an Initiator

Conformal poly(cyclohexyl methacrylate) (pCHMA) thin films were synthesized via initiated chemical vapor deposition (iCVD), with tert-butyl peroxybenzoate (TBPOB) as the initiator, representing the first time that TBPOB has been used as an initiator for iCVD synthesis. Using TBPOB instead of tert-butyl peroxide (TBPO), the rate of iCVD film growth increased by a factor of up to seven at comparable conformality and lower the filament temperature from 257 to 170 °C at a comparable deposition rate of 3 nm/min. The conformal deposition of functional thin films is desired for applications including microfluidics, medical devices and membranes. Lower filament temperatures reduce the heat load to the deposition surface and thus are advantageous for polymeric substrates that are temperature sensitive or monomers that decompose at high temperatures. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results demonstrate the similarity of the TBPOB- to the TBPO-initiated pCHMA main chains. However, the aromatic group in TBPOB provided a unique spectral signature of the polymer chain end group in the FTIR and the peak intensity increased with increase of filament temperature. Scanning electron micrographs (SEMs) revealed that the pCHMA coatings are conformal over non-planar structures; however, at identical process conditions, TBPO-initiated films showed a slightly better conformality due to the lower sticking coefficient of TBPO. At a monomer partial pressure of 0.45, TBPOB has a sticking coefficient value of 0.1188 ± 0.0092, which is ∼3 times as high as that of TBPO (0.0413 ± 0.0058). The step coverage is insensitive to filament temperature if the surface concentration of the monomer is fixed.

Molecular Layer Deposition of Functional Thin Films for Advanced Lithographic Patterning

Photoresist materials comprise one of the main challenges faced by lithography to meet the requirements of electronic device size scaling. Here we report for the first time the use of molecular layer deposition (MLD) to produce photoresist materials with controllable placement of functional moieties. Polyurea resists films are deposited by MLD using urea coupling reactions between 1,4-phenylene diisocyanate (PDIC) and ethylenediamine (ED) or 2,2'-(propane-2,2-diylbis(oxy))diethanamine (PDDE) monomers in a layer-by-layer fashion with a linear growth rate, allowing acid-labile groups to be incorporated into the film at well-controlled positions. The films are deposited with stoichiometric compositions and have highly uniform surface morphology as investigated using atomic force microscopy. We show that acid treatment can cleave the backbone of the polyurea film at positions where the acid-labile groups are embedded. We further show that after soaking the polyurea film with photoacid generator (PAG), it acts as a photoresist material and we present several UV patterning demonstrations. This approach presents a new way to make molecularly designed resist films for lithography.