Surface Of Diamond-like Carbon Thin Films Research Articles

Multifractal analysis of DLC thin films deposited by pulsed laser deposition

In this study, multifractal analysis was performed on the atomic force microscopy (AFM) images of the surface morphologies of the diamond-like carbon (DLC) thin films deposited by pulsed laser deposition (PLD) method on the silicon (Si) substrate at different substrate temperatures. In order to do this, multifractal spectra f(α) of AFM micrographs was used to characterize the surface morphology of thin films. The results obtained from multifractal spectra f(α) illustrate that the effect of substrate temperatures on the width of spectrum and ∆f is apparent. Multifractal analysis indicated that the surface of DLC thin films deposited at different substrate temperatures have a multifractal nature. It was observed that the width of the singularity spectrum, non-uniformity of the height distributions and also surface roughness of the DLC thin films increase with increasing substrate temperature. Our results clearly demonstrate that multifractal approach could efficiently describe the AFM images of the surface morphologies of the DLC thin films.

Decomposition of Perfluoropolyether Lubricant on Air Bearing Surfaces during Heat-Assisted Magnetic Recording

The thermal decomposition of a thin film of D-4OH lubricant under heating conditions on air-bearing surfaces, such as those found in magnetic recording devices, was investigated using time-of-flight secondary ion mass spectroscopy. The substrates used in this experiment were those of actual magnetic head sliders with diamond-like carbon (DLC) thin-film coatings. Two kinds of surfaces were prepared: an undisturbed DLC thin-film surface and an Al2O3 surface exposed by sputtering of the DLC thin film. Changes in the positive mass spectra as a result of heating confirmed that thermal decomposition of the D-4OH lubricant thin-film occurred, and that it was catalytically accelerated by Al2O3 at heating temperatures below 150 °C. This observation contrasts with the fact that the D-4OH lubricant thin film on the undisturbed DLC thin-film surface did not decompose.

Si incorporated diamond-like carbon film-coated electrochromic switchable mirror glass for high environmental durability

Abstract Electrochromic switchable mirror glass is promising for energy-saving windows because it changes between a reflective and a transparent state when a voltage is applied. In our previous work, we confirmed that the device degraded at high temperatures and high relative humidity using an accelerated degradation test. The degradation was related to the reaction of the moisture in atmosphere with the surface optical switching layer of the Mg–Ni thin film. Therefore, we have developed a device with a Si incorporated diamond-like carbon thin film surface layer to improve the environmental durability. When the device was kept in a simulated environment at a constant temperature of 40 °C and a constant relative humidity of 60%, optical and atomic force microscopy showed that the surface did not degrade. Moreover, the surface coating repelled water, which prevented the reaction of the moisture with the Mg–Ni thin film. The optical switching speed from the transparent state to the reflective state of the device was slower than that of the uncoated device because of the fabrication conditions. The result seems to be related to the surface of the Mg–Ni layer which might be damaged by the conditions.

Diamond-like carbon thin film with controlled zeta potential for medical material application

With the purpose of applying diamond-like carbon (DLC) thin films as a biocompatible material, we experimented with introducing functional groups such as amino and carboxyl groups to the surface of DLC thin films by plasma surface treatment. From the results, it was found that the contact angle values of the DLC thin films surface were decreased with increasing in the O C O bonded network on the surface. Measurement of the zeta potential when the amounts of the functional groups were varied showed that this successfully varied the zeta potential over the wide range of − 48 mV to + 12 mV. It was found that when carboxyl groups are introduced by O 2 plasma modification of the DLC thin films surface, the zeta potential was lower than that of untreated DLC thin films sample. It was also found that amino groups can be introduced to the DLC thin films surface by NH 3 plasma treatment, the zeta potential was higher than that of untreated DLC thin films sample. This means that zeta potential of the DLC thin films can also be controlled by controlling these two functional groups. Therefore, we have succeeded in developing a multifunctional DLC thin films that does not use polymers and is suitable as a biocompatible material.

Alignment Effects for Nematic Liquid Crystal on a New Diamond-like Carbon Layer

Alignment effects for nematic liquid crystal (NLC) and electro-optical (EO) characteristics of the ion beam (IB) aligned twisted nematic (TN)-liquid crystal display (LCD) with oblique ion beam exposure on the diamond-like carbon (DLC) thin film surface were studied. A high pretilt angle of 3.5<TEX>$^{\circ}$</TEX> in NLC by ion beam exposure on the DLC thin film layer can be measured. An excellent voltage-transmittance (V-T) curve of the ion beam aligned TN-LCD was observed with oblique ion beam exposure on the DLC thin film surface for 1 min. Also, a faster response time for the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min can be achieved.

Diamond-like Carbon 박막을 이용한 액정 배향 효과

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a diamond like carbon (DLC) thin film. A high pretilt angle of about <TEX>$3.5^{\circ}$</TEX> by ion beam(IB) exposure on the DLC thin film surface was measured. A good LC alignment by the IB alignment method on the DLC thin film surface was observed at annealing temperature of <TEX>$200^{\circ}C$</TEX>, and the alignment defect of the NLC was observed above annealing temperature of <TEX>$220^{\circ}C$</TEX>. Consequently, the high NLC pretilt angle and the good thermal stability of LC alignment by the IB alignment method on the DLC thin film surface can be achieved.