Plasma-enhanced Chemical Vapor Deposition Process Research Articles

Plasma diagnostic approach for high rate nanocrystalline Si synthesis in RF/UHF hybrid plasmas using a PECVD process

Hydrogenated nanocrystalline silicon (nc-Si : H) films intended for efficient nc-Si : H solar cells are usually made at the transition to the nanocrystalline regime using the plasma-enhanced chemical vapor deposition (PECVD) process. This change occurs within a sensitive process window and is affected by various deposition parameters. This paper reports a study of nc-Si : H films' fabrication by utilizing systematic plasma diagnostics. This work presents a novel approach for plasma processing using radio frequency (RF), ultra high frequency (UHF) and RF/UHF hybrid plasmas. Using careful analysis, efforts are made to investigate the radicals and plasma formation by changing the operating source power and silane (SiH4) concentration. The aim of this work is also to investigate the PECVD process and conditions favorable for the synthesis of nc-Si : H film. For the present study, we systematically use the optical emission spectroscopy (OES), normal, and RF-compensated Langmuir probe (LP) and vacuum ultraviolet absorption spectroscopy diagnostics. Measurements reveal that the OES diagnostic is consistent with the LP measurements. Investigation reveals that UHF power in addition to RF enables higher dissociation of H or SiH radicals and the production of higher plasma density. The combined effect of both RF and UHF sources is used as the hybrid plasma source. Measurements also reveal that inbetween SiH4 flow rates ∼20–30 sccm, there is significant change in the plasma characteristics that denotes the nc-Si : H−a-Si : H transition region. An atomic hydrogen density (nH) in the range ≈(8 − 10) × 1011 cm−3 and plasma density n0 ≈ (2 − 3) × 1011 cm−3 with a silane to hydrogen ratio of 1–2% with high crystallinity has been obtained. Along with the discussion on the effect of frequency on plasma chemistry, this explains the RF power coupling and the role of electrons and ions in plasmas with increasing frequency.

Multiscale modeling and operation of PECVD of thin film solar cells

This work proposes a multiscale modeling and operation framework for plasma-enhanced chemical vapor deposition (PECVD) of thin film silicon solar cells with uniform thickness and film surface microstructure that optimizes light trapping. Specifically, we focus on a single-wafer parallel-electrode PECVD process with showerhead arrangement and develop a multiscale model capturing both the gas-phase reaction and transport phenomena that lead to the deposition of the thin film across the wafer as well as multiple microscopic models that describe the evolution of the thin film surface microstructure at equispaced, discrete spatial locations across the wafer. While the modeling of chemical reactions and transport-phenomena (both diffusion and convection) in the gas-phase adopts the continuum hypothesis and is based on two-dimensional in space partial differential equations, a novel microscopic model is developed for the a-Si:H thin film surface evolution, which accounts for four microscopic processes: physisorption, surface migration, hydrogen abstraction and chemisorption. A hybrid kinetic Monte Carlo (kMC) algorithm is utilized to reduce computational requirements without compromising the accuracy of established chemical models that account for interactions amongst physisorbed radicals, and the microscopic model fidelity is established though calibration with experimentally obtained growth rates and surface morphology data. The results of the multiscale process model indicate that in order to produce a thin film with a diameter of 20cm and a uniform thickness with surface microstructure that optimizes light trapping: (a) a sinusoidally grated wafer surface should be used in which the grating period and depth should correspond to values that lead to film surface roughness and height–height correlation length that are on the order of visible light wavelength range, and (b) the substrate temperature should be adjusted, along several concentric zones across the substrate, to compensate for a radially non-uniform deposition rate of the film on the wafer owing to gas-phase transport phenomena. Due to the dependence of film growth rate on substrate temperature, the wafer surface is separated into four concentric zones, each with an independent heating element. Extensive simulations demonstrate that the use of appropriate sinusoidal wafer grating and the regulation of substrate temperature provide a viable and effective way for the PECVD of thin film silicon solar cells with uniform thickness and film surface microstructure that optimizes light trapping.

Copper nanowire-graphene core-shell nanostructure for highly stable transparent conducting electrodes.

A copper nanowire-graphene (CuNW-G) core-shell nanostructure was successfully synthesized using a low-temperature plasma-enhanced chemical vapor deposition process at temperatures as low as 400 °C for the first time. The CuNW-G core-shell nanostructure was systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy measurements. A transparent conducting electrode (TCE) based on the CuNW-G core-shell nanostructure exhibited excellent optical and electrical properties compared to a conventional indium tin oxide TCE. Moreover, it showed remarkable thermal oxidation and chemical stability because of the tight encapsulation of the CuNW with gas-impermeable graphene shells. The potential suitability of CuNW-G TCE was demonstrated by fabricating bulk heterojunction polymer solar cells. We anticipate that the CuNW-G core-shell nanostructure can be used as an alternative to conventional TCE materials for emerging optoelectronic devices such as flexible solar cells, displays, and touch panels.

Field electron emission enhancement of graphenated MWCNTs emitters following their decoration with Au nanoparticles by a pulsed laser ablation process

A plasma-enhanced chemical vapor deposition (PECVD) process was adapted to alter the growth of multiwall carbon nanotubes (MWCNTs) so that graphene sheets grow out of their tips. Gold nanoparticle (Au-NP) decoration of graphenated MWCNTs (g-MWCNTs) was obtained by subsequent decoration by a pulsed laser deposition (PLD) process. By varying the number of laser ablation pulses (NLp) in the PLD process, we were able to control the size of the gold nanoparticles and the surface coverage of the decorated g-MWCNTs. The presence of Au-NPs, preferentially located at the tip of the g-MWCNTs emitters, is shown to significantly improve the field electron emission (FEE) properties of the global g-MWCNT/Au-NP nanohybrid films. Indeed, the electric field needed to extract a current density of 0.1 μA cm−2 from the g-MWCNT/Au-NP films was decreased from 2.68 V μm−1 to a value as low as 0.96 V μm−1. On the other hand, UV photoelectron spectroscopy (UPS) characterization revealed a decrease in the global work function of the Au-decorated g-MWCNT nanohybrids compared to that of bare g-MWCNT emitters. Surprisingly, the work function of g-MWCNT was found to decrease from 4.9 to 4.7 eV with the addition of Au-NPs—a value lower than the work function of both materials worth 5.2 and 4.9 eV for gold and g-MWCNT, respectively. Our results show that the NLp dependence of the FEE characteristics of the g-MWCNT/Au-NP emitters correlates well with their work function changes. Fowler-Nordheim-theory-based calculations suggest that the significant FEE enhancement of the emitters is also caused by the Au-NPs acting as nanoscale electric field enhancers.

PECVD와 NO 어닐링 공정을 이용하여 제작한 N-based 4H-SiC MOS Capacitor의 SiC/SiO2 계면 특성

본 연구에서는 4H-SiC MOSFET의 주요 문제점인 <TEX>$SiC/SiO_2$</TEX> 계면의 특성을 향상시키기 위해 PECVD (plasma enhanced chemical vapor deposition) 공정을 이용하여 n-based 4H-SiC MOS Capacitor를 제작하였다. 건식 산화 공정의 낮은 성장속도, 높은 계면포획 밀도와 <TEX>$SiO_2$</TEX>의 낮은 항복전계 등의 문제를 극복하기 위하여 PECVD와 NO어닐링 공정을 사용하여 MOS Capacitor를 제작하였다. 제작이 끝난 후, MOS Capacitor의 계면특성을 hi-lo C-V 측정, I-V 측정 및 SIMS를 이용해 측정하고 평가하였다. 계면의 특성을 건식 산화의 경우와 비교한 결과 20% 감소한 평탄대 전압 변화, 25% 감소한 <TEX>$SiO_2$</TEX> 유효 전하 밀도, 8MV/cm의 증가한 <TEX>$SiO_2$</TEX> 항복전계 및 1.57eV의 유효 에너지 장벽 높이, 전도대 아래로 0.375~0.495eV만큼 떨어져 있는 에너지 영역에서 69.05% 감소한 계면 포획 농도를 확인함으로써 향상된 계면 및 산화막 특성을 얻을 수 있었다. In this research, n-based 4H-MOS Capacitor was fabricated with PECVD (plasma enhanced chemical vapor deposition) process for improving SiC/<TEX>$SiO_2$</TEX> interface properties known as main problem of 4H-SiC MOSFET. To overcome the problems of dry oxidation process such as lower growth rate, high interface trap density and low critical electric field of <TEX>$SiO_2$</TEX>, PECVD and NO annealing processes are used to MOS Capacitor fabrication. After fabrication, MOS Capacitor's interface properties were measured and evaluated by hi-lo C-V measure, I-V measure and SIMS. As a result of comparing the interface properties with the dry oxidation case, improved interface and oxide properties such as 20% reduced flatband voltage shift, 25% reduced effective oxide charge density, increased oxide breakdown field of 8MV/cm and best effective barrier height of 1.57eV, 69.05% reduced interface trap density in the range of 0.375~0.495eV under the conduction band are observed.

Microstructure and properties of silicon-incorporated DLC film fabricated using HMDS gas and RF-PECVD process.

The microstructure and characteristics of silicon-incorporated diamond-like carbon film, fabricated using a radio-frequency plasma-enhanced chemical vapor deposition process with hexamethyldisilane [(CH3)3,Si x Si(CH3)3:HMDS] gas as a silicon source, were investigated. Diamond-like carbon films with silicon compositions from 0 to 5 atomic percent were deposited onto ultra-fine grained AZ31 magnesium alloy substrate as buffer layers or multilayers. Si doping led not only to an increase in the bonding ratio (sp3/sp2), but improvements in hardness, critical adhesion, and corrosion resistance. Out of the investigated samples, the multi-deposited silicon diamond-like carbon thin film on magnesium substrate showed the best combination of adhesive, wear resistance, and corrosion resistance properties.

Effect of catalyst film thickness on the structures of vertically-oriented few-layer graphene grown by PECVD

The growth behavior of vertically-oriented few-layer graphene (V-FLG), produced by radio-frequency plasma enhanced chemical vapor deposition (PECVD), is studied here as a function of catalyst and catalyst film thickness. The Co catalyst and catalyst film thickness were observed as being crucial for the growth states and morphology of V-FLG. V-FLG showed a slower growth rate and lower density on substrates without catalyst than with catalyst due to the V-FLG nucleation on the former being prevented. It demonstrates that the growth mechanism of V-FLG on the Co catalyst film is not similar to the catalytic growth mechanism of CNTs, which is a defect nucleation mechanism. During PECVD process, the highly reactive C radicals can preferentially form CNTs or graphite-shell by Co catalysis, then trigger nucleation on the surface of CNTs or graphite-shell for V-FLG growth. The excellent field emission properties of the V-FLG and FLG-CNTs make them promising candidates for high-performance field emission emitters.

Low Cost, Scalable and Selective Electrochemical TSV Fill Technology for 3D IC Interconnects

Physical and economical limitations for 2D scaling (so called “Moore’s Law”) prevents further increase of integration density to improve the performance of integrated circuits (IC). These challenges have stimulated the development of 3D through-silicon via (TSV) technology (so called “More than Moore”) in order to increase the speed and the bandwidth of the devices as well as to decrease the form factor and power consumption of integrated microsystems. However, the implementation of 3D TSV technology is limited by the high cost of 3D TSV fill (due to the use of expensive vapor deposition and chemical-mechanical processes) and its poor scalability (due to low conformality of physical and chemical vapor deposited films) to high TSV aspect ratios and smaller via sizes (to increase I/O). The objective of this investigation is to address the cost and scalability issues in order to enable cost-effective and reliable fill of high aspect ratio 3D TSVs. In this paper, we will review the low temperature and scalable process technology for 3D TSV fill employing the selective electrochemical through-via metal (Ni alloy/Cu or Co alloy/Cu) filling technology which is more economical because it will eliminate expensive chemical-mechanical polishing (CMP) process and replace expensive plasma-enhanced chemical vapor deposition (PE CVD) and physical vapor deposition (PVD) processes with low cost, lower temperature (<100 oC), more scalable (AR > 30:1) selective electrochemical process (LoCoSS process). LoCoSS process technology includes the following major electrochemical process steps: anodic oxidation to form isolation layer, selective electroless barrier deposition and selective electrochemical fill that can be implemented using one LoCoSS electrochemical processing tool instead of four POR processing tools utilizing different technologies – PE CVD isolation, PVD barrier/seed, Electrofill and CMP.The activation of thin continuous electroless barrier films (Ni or Co alloys) with high adhesion on the isolation surface (SiO2) is challenging. To overcome this technical risk, a novel nanoactivation process has been developed with the use of self-assembled monolayers [Si-(CH2)x-NH2-OH] and catalytic functionalized nanoparticles (Pd/Cu). To increase the adhesion of the deposited barrier films, the covalent bonding between substrate and the SAM binding layer has been engineered through the proper choice of the functional groups. Selective activation has been achieved through the mechanical removal of catalysts from the front surface (except inside the TSV’s) and the use of photosensitive TiO2/catalyst process. Besides, robust and defect-free fill of high aspect ratio TSV’s requires the development of electroless Cu superfill process with the use of suppressing additives in the plating solution such as high molecular weight polyacrylic acid (PAA) and polyethylene glycols (PEG). Selective electroless Cu plating into high aspect ratio TSV was successfully demonstrated with complete coverage of electroless barrier layer and low overplating on the field. Copper electroplating from NANO3D suppression-based plating solutions was also used to enable high speed and uniform plating of flat Cu bumps that can be used to interconnect chips in 3D microelectronics systems. LoCoSS technology could accelerate the mass-scale adoption of low cost and scalable TSV technology in semiconductor manufacturing. Implementation of our proprietary LoCoSS process will lower the cost of 3D ICs with the potential to reduce the cost by over 2X and increase scalability by over 3X for volume production. Besides, enabling low cost 3D ICs with our technology will allow heterogeneous system generation for next generation smart phones and other communication devices as well as increase of the bandwidth, memory capacity and decrease of the signal transmission delay within computing chips.

Inductively coupled plasma chemical vapor deposition silicon nitride for passivation of In0.83Ga0.17As photodiodes

Silicon nitride films (SiNx) deposited by ICPCVD (inductively coupled plasma chemical vapor deposition) at lower temperature (75°C) are investigated on extended wavelength In0.83Ga0.17As photodiodes. Compared to SiNx films (330°C) grown by PECVD (plasma enhanced chemical vapor deposition), the low-temperature-deposited SiNx films grown by ICPCVD have a better effect on decreasing the dark current of In0.83Ga0.17As photodiodes. Area- and perimeter-dependent leakage current were separated by test arrays with different area photosensitive elements. The results indicate that the perimeter-dependent leakage current is obviously decreased for the devices passivated by ICPCVD. The analysis of activation energy indicates that the area-dependent leakage current is dominated by diffusion and generation-recombination mechanisms at reverse bias of 0.1–0.5V and temperature of 260–300K for both ICPCVD and PECVD processes. At reverse bias of 0.1–0.5V and temperature of 200–300K the perimeter-dependent leakage current is dominated by surface recombination current mechanism for ICPCVD, while it is dominated by ohmic current and surface recombination current mechanisms for PECVD. The cause of the reduction of perimeter-dependent leakage current for ICPCVD may derive from its better restraint of ohmic current.

Hierarchical hematite nanoplatelets for photoelectrochemical water splitting.

A new nanostructured α-Fe2O3 photoelectrode synthesized through plasma-enhanced chemical vapor deposition (PE-CVD) is presented. The α-Fe2O3 films consist of nanoplatelets with (001) crystallographic planes strongly oriented perpendicular to the conductive glass surface. This hematite morphology was never obtained before and is strictly linked to the method being used for its production. Structural, electronic, and photocurrent measurements are employed to disclose the nanoscale features of the photoanodes and their relationships with the generated photocurrent. α-Fe2O3 films have a hierarchical morphology consisting of nanobranches (width ∼10 nm, length ∼50 nm) that self-organize in plume-like nanoplatelets (350-700 nm in length). The amount of precursor used in the PE-CVD process mainly affects the nanoplatelets dimension, the platelets density, the roughness, and the photoelectrochemical (PEC) activity. The highest photocurrent (j = 1.39 mA/cm(2) at 1.55 VRHE) is shown by the photoanodes with the best balance between the platelets density and roughness. The so obtained hematite hierarchical morphology assures good photocurrent performance and appears to be an ideal platform for the construction of customized multilayer architecture for PEC water splitting.

Monitoring of powder formation via optical emission spectroscopy and self-bias-voltage measurements for high depletion μc-Si:H deposition regimes

Microcrystalline silicon fabricated by plasma-enhanced chemical vapour deposition (PECVD) is commonly used as an absorber material in thin-film tandem solar cells. The source gases used in the μc-Si:H PECVD process are silane and hydrogen. One way to further increase the production efficiency of solar modules is to increase the gas utilization during deposition of the silicon absorber layer. In this work this is achieved by reducing the hydrogen flow. These deposition conditions are known to promote powder formation in the plasma, which can be detrimental for the solar cell’s conversion efficiency as well as for the maintenance of the system. Therefore, an easily applicable approach to determine powder formation in-situ during the PECVD process is presented. Both the self-bias-voltage and the ratio of the optical emissions from SiH* to Hβ as function of the gas residence time in the plasma is used to determine the onset of powder formation. Furthermore, a clear link between the precursor gas residence time in the plasma to the onset of powder formation is shown independent of the chosen pressure.

Enhancement of photocatalyic activity of dye sensitised anatase layers by application of a plasma-polymerized allylamine encapsulation

Abstract A polyallylamine coating was applied as a protective encapsulation to iridium dye sensitised TiO 2 catalyst layers by a plasma-enhanced chemical vapour deposition process. A significant enhancement of the incident-photon-to-current efficiencies of the polymer-confined dye/catalyst assembly was observed, with a strong dependence on the nominal thickness of the polymer-coating. An optimum thickness of the polyallylamine coating between 15 and 50 nm was obtained with regard to photoefficiency of the polymer-coated dye/TiO 2 catalyst in a neutral electrolyte. Results are discussed in terms of porosity and electrolyte permeability of the plasma polymer layer.

Tuning oxygen impurities and microstructure of nanocrystalline silicon photovoltaic materials through hydrogen dilution.

As a great promising material for third-generation thin-film photovoltaic cells, hydrogenated nanocrystalline silicon (nc-Si:H) thin films have a complex mixed-phase structure, which determines its defectful nature and easy residing of oxygen impurities. We have performed a detailed investigation on the microstructure properties and oxygen impurities in the nc-Si:H thin films prepared under different hydrogen dilution ratio treatment by the plasma-enhanced chemical vapor deposition (PECVD) process. X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and optical transmission spectroscopy have been utilized to fully characterize the microstructure properties of the nc-Si:H films. The oxygen and hydrogen contents have been obtained from infrared absorption spectroscopy. And the configuration state of oxygen impurities on the surface of the films has been confirmed by X-ray photoelectron spectroscopy, indicating that the films were well oxidized in the form of SiO2. The correlation between the hydrogen content and the volume fraction of grain boundaries derived from the Raman measurements shows that the majority of the incorporated hydrogen is localized inside the grain boundaries. Furthermore, with the detailed information on the bonding configurations acquired from the infrared absorption spectroscopy, a full explanation has been provided for the mechanism of the varying microstructure evolution and oxygen impurities based on the two models of ion bombardment effect and hydrogen-induced annealing effect.

Plasma Enhanced Chemical Vapor Deposition Time Effect on Multi-Wall Carbon Nanotube Growth Using C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt; as Precursors

Multi-wall carbon nanotube (MWCNT) structures were grown on cobalt catalyst layer through Plasma Enhanced Chemical Vapor Deposition (PECVD) process. Acetylene (C2H2) and hydrogen (H2) are used as precursors during the PECVD process. The morphology structures of the MWCNTs grown under different PECVD time were investigated and characterized using Scanning Electron Microscope (SEM). The effect of the PECVD time on the MWCNT growth is studied by varying the PECVD time at 45 sec and 600 sec. The morphology structures suggest that the growth rate is proportional to the PECVD time under the similar setting condition of pressure, acetylene flow-rate and temperature.

Direct observation and mechanism for enhanced electron emission in hydrogen plasma-treated diamond nanowire films.

The effect of hydrogen plasma treatment on the electrical conductivity and electron field emission (EFE) properties for diamond nanowire (DNW) films were systematically investigated. The DNW films were deposited on silicon substrate by N2-based microwave plasma-enhanced chemical vapor deposition process. Transmission electron microscopy depicted that DNW films mainly consist of wirelike diamond nanocrystals encased in a nanographitic sheath, which formed conduction channels for efficient electron transport and hence lead to excellent electrical conductivity and EFE properties for these films. Hydrogen plasma treatment initially enhanced the electrical conductivity and EFE properties of DNW films and then degraded with an increase in treatment time. Scanning tunneling spectroscopy in current imaging tunneling spectroscopy mode clearly shows significant increase in local emission sites in 10 min hydrogen plasma treated diamond nanowire (DNW10) films as compared to the pristine films that is ascribed to the formation of graphitic phase around the DNWs due to the hydrogen plasma treatment process. The degradation in EFE properties of extended (15 min) hydrogen plasma-treated DNW films was explained by the removal of nanographitic phase surrounding the DNWs. The EFE process of DNW10 films can be turned on at a low field of 4.2 V/μm and achieved a high EFE current density of 5.1 mA/cm(2) at an applied field of 8.5 V/μm. Moreover, DNW10 films with high electrical conductivity of 216 (Ω cm)(-1) overwhelm that of other kinds of UNCD films and will create a remarkable impact to diamond-based electronics.

Transformation of polymer composite nanofibers to diamond fibers and films by microwave plasma-enhanced CVD process

In this work, polyvinyl alcohol (PVA) fibers were used as a polymer matrix containing ultra-dispersed diamond (UDD) nanoparticles. Growth of diamond fiber-like structures and films by microwave plasma-enhanced chemical vapor deposition was studied as a function of UDD concentration in the PVA matrix. The influence of surface tension (fibers radii) for nucleation/seeding is discussed. Using a high UDD concentration in the polymer matrix lead to the formation of fiber-like structures. The composite PVA polymer nanofibers with the highest concentration of UDD nanoparticles resulted in the growth of nearly continuous diamond film at low thickness of 250 nm.

An integrated Mach–Zehnder interferometric biosensor with a silicon oxynitride waveguide by plasma-enhanced chemical vapor deposition

We report the design and fabrication of an integrated Mach–Zehnder interferometric (MZI) biochip based on silicon oxynitride layers deposited with a plasma-enhanced chemical vapor deposition (PECVD) process. A rib waveguide for an integrated MZI sensor has been designed to have a high surface sensitivity and a single-mode behavior by using an effective index method. The integrated MZI chip operating at 637 nm is fabricated via conventional photolithography and reactive ion etching. As a biosensor application, the real-time and label-free detection of the covalent immobilization and hybridization of DNA strands is performed and verified with this device.

Applications of µc-SiOx:H as integrated n-layer and back transparent conductive oxide for a-Si:H/µc-Si:H tandem cells

We have prepared n-type hydrogenated microcrystalline silicon oxide [µc-SiOx:H(n)] films with oxygen contents from 0 to 37.3 at. % by varying the CO2-to-SiH4 flow ratio in a plasma-enhanced chemical vapor deposition (PECVD) system. By using µc-SiOx:H(n) as an effective replacement for integrated µc-Si:H(n) and indium–tin oxide (ITO), µc-Si:H single-junction and a-Si:H/µc-Si:H tandem cells exhibited significantly improved efficiencies of 6.35 and 10.53%, respectively. The improvement of the single-junction and tandem cells mainly arose from the enhancement of long-wavelength optical absorption in µc-Si:H absorbers, which was confirmed by a quantum efficiency instrument showing a markedly enhanced spectral response at wavelengths from 600 to 1100 nm. Moreover, all the PECVD processes, except the metal contact, had an advantage of in situ deposition without breaking vacuum, thereby minimizing contamination of the interface. The simplified cell fabrication can enhance the fill factor, which will benefit industrial production.

Photoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films

Silicon quantum dots (QDs) embedded in hydrogenated amorphous Si-rich silicon carbide (α-SiC:H) thin films were realized by plasma-enhanced chemical vapor deposition process and post-annealing. Fluorescence spectroscopy was used to characterize the room-temperature photoluminescence properties. X-ray photoelectron spectroscopy was used to analyze the element compositions and bonding configurations. Ultraviolet visible spectroscopy, Raman scattering, and high-resolution transmission electron microscopy were used to display the microstructural properties. Photoluminescence measurements reveal that there are six emission sub-bands, which behave in different ways. The peak wavelengths of sub-bands P1, P2, P3, and P6 are pinned at about 425.0, 437.3, 465.0, and 591.0 nm, respectively. Other two sub-bands, P4 is red-shifted from 494.6 to 512.4 nm and P5 from 570.2 to 587.8 nm with temperature increasing from 600 to 900 °C. But then are both blue-shifted, P4 to 500.2 nm and P5 to 573.8 nm from 900 to 1200 °C. The X-ray photoelectron spectroscopy analysis shows that the samples are in Si-rich nature, Si-O and Si-N bonds consumed some silicon atoms. The structure characterization displays that a separation between silicon phase and SiC phase happened; amorphous and crystalline silicon QDs synthesized with increasing the annealing temperature. P1, P2, P3, and P6 sub-bands are explained in terms of defect-related emission, while P4 and P5 sub-bands are explained in terms of quantum confinement effect. A correlation between the peak wavelength shift, as well as the integral intensity of the spectrum and crystallization of silicon QDs is supposed. These results help clarify the probable luminescence mechanisms and provide the possibility to optimize the optical properties of silicon QDs in Si-rich α-SiC: H materials.

Low pressure plasma modified polycarbonate: A transparent, low reflective and scratch resistant material for automotive applications

Abstract During the last years, the employment of light polymeric materials, to replace those commonly used in the automotive industry, has been investigated by many equipment manufacturers. Polymeric glazing, e.g. polycarbonate, are desirable because of their ability to reduce weight and fuel consumption, while providing good optical properties and impact resistance. In this paper, we report a two steps low pressure plasma treatment composed by an etching, optimized for the nano-texturing of polycarbonate to improve its anti-reflective property by simulating the so-called “Moth eye” effect, and by a plasma enhanced-chemical vapour deposition process to enhance the scratch resistance. Reflectance/transmittance measurements showed that this approach is able to increase the anti-reflective property of the polycarbonate without drastically damaging its transmittance, while scratching test by “car wash” simulator demonstrated the increase of scrape resistance. The haze test confirmed the transparency of the plasma treated polymer also after washing.