Plasma CVD Technique Research Articles

Few layers isolated graphene domains grown on copper foils by microwave surface wave plasma CVD using camphor as a precursor

Few layers isolated graphene domains were grown by microwave surface wave plasma CVD technique using camphor at low temperature. Graphene nucleation centers were suppressed on pre-annealed copper foils by supplying low dissociation energy. Scanning electron microscopy study of time dependent growth reveals that graphene nucleation centers were preciously suppressed, which indicates the possibility of controlled growth of large area single crystal graphene domains by plasma processing. Raman spectroscopy revealed that the graphene domains are few layered which consist of relatively low defects.

Defect-induced strain relaxation in 3C-SiC films grown on a (100) Si substrate at low temperature in one step

The epitaxial deposition of a 3C-SiC film on a (100) Si substrate has been achieved at low temperature in one step using the microwave plasma CVD technique. A high density of defects such as misfit dislocations, stacking faults (SF) and twin boundaries (TB) is generated in the film. Defect-induced strain distribution in the 3C-SiC film is analyzed by the geometric phase analysis (GPA) method combined with X-ray diffraction (XRD) and Raman spectroscopy. The strain analysis at an atomic level reveals that periodical misfit dislocations at the interface generate high local compressive strain (>20%) around the core of the dislocations in the SiC film, relaxing the major part of the intrinsic strain. A highly compressive interfacial layer is found to form between the SiC film and Si substrate regardless of the carbonization temperature. This interfacial layer is linked with the carbonization step of the film growth process. In addition, twins and stacking faults provide a complementary route for strain relaxation during the film growth process. It is found that more strain is accommodated at the matrix/twin interface during twin nucleation rather than that at the growth stage. The atomic understanding of the effects of crystalline defects on strain relaxation will provide important implications for the control of defects in SiC films and design of high-performance SiC devices.

Si-doped nano- and microcrystalline diamond films with controlled bright photoluminescence of silicon-vacancy color centers

Nanocrystalline diamond (NCD) and microcrystalline diamond (MCD) films with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738nm have been grown using a microwave plasma CVD technique. The films were doped with Si via adding silane to CH4–H2 reaction gas mixture in the course of the deposition process. The dependence of SiV PL intensity on silane concentration in gas shows a maximum at SiH4/CH4 ratios of 0.2% and 0.6% for NCD and MCD films, respectively, the maximum intensity for MCD being an order of magnitude stronger compared with that for NCD. The PL quenching at higher CH4 addition occurs, however, no significant degradation of the film structure, such as Si-induced amorphous carbon formation, was observed within the SiH4 concentration range studied (0%–0.9%). The higher PL efficiency of the MCD films is related to their less defective structure, as deduced from Raman spectroscopy analysis.

Panasonic’s Thin Film Silicon Technologies for Advanced Photovoltaics

ABSTRACTWe have fabricated high-efficiency a-Si/µc-Si tandem solar cells and modules with a very high µc-Si deposition rate using Localized Plasma Confinement CVD to give very high-rate deposition (>2.0 nm/s) of device-grade µc-Si layers. For further progress in productive plasma-CVD techniques, we have studied plasma phenomena by combining newly developed plasma simulation and plasma diagnosis techniques that reveal the importance of non-emissive atomic hydrogen. We also have proposed a model of defective µc-Si formation on highly textured substrates in which the atomic H in plasma is assumed to play an important role. We are also developing a non-vacuum deposition technique that we term “Liquid Si Printing.” A new record conversion efficiency for HIT solar cells of 24.7% has been achieved using a very thin c-Si wafer (Thickness: 98 µm, Area: 102 cm2).

Synthesis of graphene by surface wave plasma chemical vapor deposition from camphor

AbstractWe demonstrate synthesis of graphene using the solid precursor camphor in a microwave excited surface wave plasma chemical vapor deposition technique. Highly sublimely camphor was introduced into the plasma chamber in the vapor phase along with Ar and uniform plasma formation was obtained. Rapid deposition of a graphene film on Cu foil was achieved at a relatively low temperature (<600 °C). Raman spectroscopy and transmission electron microscopy clearly showed that the deposited film on Cu foil consist of few‐layer graphene. Fully flexible transparent electrode was fabricated by transferring the graphene film with excellent properties for device application. magnified imageSynthesis of large‐area graphene film from solid botanical derivative camphor (C10H16O) in a surface wave microwave plasma CVD technique.

Low Temperature Growth of Carbon Nanomaterials on the Polymer Substrate Using Ion Assisted Microwave Plasma CVD

In this study, the successful growth of carbon nanotubes and few-layered graphene sheets on the silicon and polyimide substrates at relatively low temperature of 230-260°C by microwave surface wave plasma CVD technique has been demonstrated. Graphite-encapsulated Ni nanoparticles have been used as the catalyst for growing carbon nanomaterials (CNMs) in NH3/CH4 plasma. The results of high-resolution transmission electron microscope(TEM) analysis show the effect of substrate on the structure of CNMs.

Homoepitaxial growth of high quality thick diamond film with microwave plasma CVD technique

AbstractA growth of high quality thick diamond film has been carried out on high pressure and high temperature diamond substrate by microwave plasma chemical vapor deposition system. First, the effect of growth parameters on the growth film morphologies was investigated, indicating that the diamond film is very sensitive to the growth temperature and input microwave power. Then, sample holders with different geometries were used in our experiment, illustrating that high quality diamond film can be grown by using the sample holder with flat surface. Finally, the characterization of the as grown samples has been carried out.

PEMBUATAN PADUAN (Ti1-xAlx)N DENGAN TEKNIK PLASMA CVD DARI BUBUK AlCl3, GAS N2 DAN H2, SERTA LARUTAN TiCl4

n n The substitution of Ti atoms by Al atoms in TiN lattice sites to form (Ti1-xAlx)N is clearly demonstrated by the coatings which were deposited on steel substrate and using plasma CVD technique. The presence of Al atoms in TiN lattice site is shown by means of XRD and EDX techniques: lattice parameters decreasing of TiN as the fraction of Al increases (XRD) and precipitation of hexagonal AlN phase (XRD) as the fraction of Al exceeding 0.8 (EDX). The hardness of these coating are just around 30 GPa, which is beyond the values reported in literatures.

Structural, optical and secondary electron emission properties of diamond like carbon thin films deposited by pulsed-DC plasma CVD technique

Plasma enhanced chemical vapor deposition (PECVD) technique using pulsed-DC power supply was used to fabricate diamond like carbon (DLC) films at deposition rates as high as 110 nm/min. The DLC films deposited by pulsed-DC and DC based power supplies under different gas flow ratios were studied for their suitability as dielectric layer coatings in plasma display panels (PDPs). The effect of deposition parameters on the properties of the DLC films were studied using Fourier transform infra-red spectroscopy (FTIR) and spectroscopic ellipsometry (SE). FTIR reveals that higher hydrogen dilution in gas mixture leads to higher sp 3 content. SE studies in wide spectral range were analyzed using Tauc-Lorentz model dielectric function. A rise in the extracted refractive index was seen on increasing the H 2 content in the feed gas, thus resulting in optically denser films. Secondary electron emission coefficient ( γ) was measured in the films deposited by the DC and pulsed-DC based PECVD. Firing voltage in the DLC samples was found to have very low variation in the operating pressure range used in commercial PDPs, suggesting possibility of enhanced long term reliability of DLC coatings in future PDP applications.

Diamond mosaic crystals for neutron instrumentation: First experimental results

Diamond single crystals were recently proposed as monochromators of unprecedented performance [1] (Freund, 2009). In the present paper we describe how diamond crystals with a suitable mosaic spread can be produced using a specific plasma CVD technique. Up to 2mm thick samples with an average mosaic spread of 0.2° have been produced. We report on X- and gamma-ray characterisation checking the uniformity of the mosaic structure and present the results of a first study regarding the neutron reflection properties of this outstanding material. These promising results show that the diamond diffraction properties are not too far from the theoretical expectations. For example, 34% peak reflectivity has been obtained for a 1mm thick crystal at 1Å wavelength.

Correlation of structural inhomogeneities with transport properties in amorphous silicon germanium alloy thin films

Amorphous silicon–germanium (a-Si 1− x Ge x :H) alloy thin films were studied over a wide range of Ge content ( x=0–1.00) grown by radio frequency plasma CVD (rf PECVD) technique with variation of different deposition parameters such as H 2 dilution, rf power and square wave pulse modulation (SWPM) of rf amplitude. Structural properties like microstructure factor ( R ⁎) and AFM surface roughness ( R RMS ) were correlated with the transport properties such as mobility-lifetime product ( μτ) and ambipolar diffusion length ( L d ) of these films. Near the middle composition range ( x=0.32–0.70), the R ⁎ in these films varies between 0.20 and 0.42 and L d ranges between 50 and 60 nm. Films deposited near the pure silicon and pure germanium ends have improved structural and transport properties. By SWPM method we have been able to significantly lower the R ⁎ value of the a-Si 1− x Ge x :H films to 0.15 with x=0.40–0.45 resulting in L d =100 nm and μτ=1.0×10 −6 cm 2 V −1.

Impact of film structure on damage to low-k SiOCH film during plasma exposure

We investigated the resistance of a low-k SiOCH film structure to plasma-irradiation damage by comparing films deposited by neutral-beam enhanced chemical-vapour-deposition (NBECVD) and conventional plasma CVD techniques to clarify the degradation mechanism of the dielectric constant in low dielectric SiOCH film during plasma etching. We found that the durability of a low-k SiOCH film structure to plasma irradiation strongly depended on the kind of Si–O structure the film had. In particular, a linear Si–O structure was less affected by plasma exposure than were network/cage Si–O structures because of the small amount of stress in the O–Si–O structure. In addition, this linear Si–O structure helped to reduce the number of methyl groups removed from the film by plasma irradiation, which preserved the dielectric constant. Since the NBECVD technique can generate a low-k SiOCH film with more linear Si–O structures than conventional plasma CVD, a film made through this technique has very strong plasma durability.

Cross-sectional hydrogen content and mass density profiles of diamond-like carbon film by neutron and X-ray reflectivity

The cross-sectional profiles of hydrogen content and mass density of diamond-like carbon (DLC) film were investigated using X-ray and neutron reflectivity. DLC films were prepared using a plasma CVD technique by varying the H 2/(H 2 + CH 4) ratio gas source from 0 to 0.9. The cross-sectional hydrogen content and mass density profiles of the films were calculated by neutron and X-ray reflectivity, and the results were compared with those from elastic recoil detection analysis (ERDA). The fitted simulation showed that the mass density gradually decreased with increasing depth, whereas the hydrogen content increased with depth. In both ERDA and reflectivity measurements, the average hydrogen content was more than 30% in all films and tended to increase with the H 2/(CH 4 + H 2) ratio. However, there was a difference in hydrogen content values between the two analyses ranging from 5.1 % to 8.5%.

Surface plasmon characteristics of nanocrystalline gold/DLC composite films prepared by plasma CVD technique

Composite films containing gold nanoparticles embedded in diamond-like carbon (Au–DLC) matrix were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction varied between 2.7–3.5 nm and 0.04–0.7, respectively with the amount of argon in the methane + argon gas mixture in the plasma. Bonding environment in these films were obtained from XPS, Raman and FTIR studies. Microstructural studies were carried out by SEM, XRD and TEM studies. Blue-shift of the surface plasmon resonance peak (located ∼540–561 nm) in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was associated with the increase in volume fraction of metal particles. The experimental results have been discussed in light of the core–shell model.

Synthesis and characterization of composite films of silver nanoparticles embedded in DLC matrix prepared by plasma CVD technique

Composite films containing silver nanoparticles embedded in diamond-like carbon (DLC) matrix were deposited on glass substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition techninique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of methane of a gas mixture of methane + argon in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and FTIR studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was associated with the increase in volume fraction of metal particles. The experimental results have been discussed in light of the existing Mie theory.

Characterization of nanocrystalline gold/DLC composite films synthesized by plasma CVD technique

Composite films containing gold nanoparticles embedded in diamond-like carbon (Au–DLC) matrix were deposited on glass and Si (1 0 0) substrates by using capacitatively coupled plasma (CCP) chemical vapour deposition technique (CVD). Particle size and metal volume fraction were tailored by varying the relative amount of argon in the methane + argon gas mixture in the plasma. Optical constants of the films were evaluated. Bonding environment in these films were obtained from Raman and Fourier transformed infrared spectra (FTIR) studies. Blue-shift of the surface plasmon resonance peak in the optical absorbance spectra of the films could be associated with the reduction of the particle size while red shift was observed with the increase in volume fraction of metal particles in the DLC films. Absorption spectra recorded in the reflection mode indicated dichromatism in these films.

Seeding of polymer substrates for nanocrystalline diamond film growth

Nanocrystalline diamond (NCD) thin films and structures are grown by microwave plasma CVD technique on SiO 2/Si substrates patterned by polymer. The substrates are seeded by ultra-dispersed diamond (UDD) nanoparticles in polymer, by spin coating of UDD drop and by ultrasonic treatment in solution of UDD. For all samples, the deposited NCD film is strongly related to the primary polymer deposited over the Si/SiO 2 substrate. For a certain concentration of UDD, seeding by polymer composite results in formation of fully closed layer. The drop of UDD requires using of spin coating process and by repeating of this procedure, a NCD layer with clear 3D geometry is achieved. Ultrasonic treatment leads in “implanting” of UDD into the polymer bulk. The primary polymer stripes are damaged during this procedure. In addition, 3D porous like layer is observed after the CVD growth. Optimizing the seeding procedure and the dimension of the primary polymer allow a direct growth of self-standing air bridges suitable for MEMS/NEMS applications.

Biocompatibility of a-C:H film coating for synthetic vascular graft

Amorphous hydrogenated carbon (a-C:H) films have many excellent properties such as biocompatibility, anti-corrosion, and chemical stability. Therefore, there are many reports on application of a-C:H film as surface modification technique for biomaterials. However, it is difficult to deposit a-C:H film on complex structures such as artificial heart blood pump and synthetic vascular grafts. In our previous work, we have developed an electrode which is adapted to such irregular structures for plasma CVD technique. In this study, a-C:H film was deposited on a synthetic vascular graft inner-wall by r.f. plasma CVD technique with cylindrical electrode. The purpose of such coating is improvement of biocompatibility of the vascular graft. The biocompatibility of the a-C:H film was evaluated by cytocompatibility and plasma protein adhesion. For the a-C:H film deposition, cytocompatibility and protein adsorbent of the vascular grafts were improved for biological response under cell culture with mouth fibroblasts and plasma proteins (albumin, fibrinogen, and globulin), respectively. This study indicates that the a-C:H films coatings is expected to surface modification for medical appliances.

Microstructural and optical properties of BN films deposited by inductively coupled plasma CVD

Boron nitride films were deposited at different substrate temperatures (400–600 K) on Si (100) substrates by RF plasma CVD technique using a mixture of borane-ammonia, argon and nitrogen as the precursor gases. No intentional bias was applied during deposition to modulate the ion energy. The surface textures of the films were obtained by Atomic Force Microscope studies (AFM). X-ray Photoelectron Spectroscopy (XPS) studies were carried out to determine the bonding environment in the coatings. Fourier Transformed Infra-Red (FTIR) spectrums indicated that the films deposited at lower substrate temperature contained h-BN phases and the percentage of c-BN content in the films increased with the substrate temperature. Films deposited at temperature ∼553 K were predominantly c-BN in nature.

Catalytic Induced Thermal Conversion of Amorphous Carbon into Single Walled Carbon Nanotubes

AbstractSingle walled carbon nanotubes (SWNTs) have caught extensive attention in the field of material science and electronics. Their formation typically uses plasma arc or CVD techniques [1–3]. So far, formation of SWCNTs just by thermal conversion of amorphous, non graphitic carbon which is a nearly ubiquitous carbon source is challenging but has not been reported so far. We herein demonstrate the catalytic growth of SWNTs from an amorphous carbon source (activated charcoal powder, ‘Aktivkohle’) mediated by three different catalytically active metals; metallic nickel, nickel derived from bis(η5‐cyclopentadienyl)nickel (nickelocene) and yttrium formed in situ from yttrium oxide.