Characteristics and Electrical Properties of SiNx:H Films Fabricated by Plasma-Enhanced Chemical Vapor Deposition

SiNx：H films with different N/Si ratios are synthesized by plasma-enhanced chemical vapor deposition （PECVD）. Composition and structure characteristics are detected by Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）. It indicates that Si-N bonds increase with increased NH3/SiH4 ratio. Electrical property investigations by I-V measurements show that the prepared films offer higher resistivity and less leakage current with increased N/Si ratio and exhibit entirely insulating properties when N/Si ratio reaches 0.9, which is ascribed to increased Si-N bonds achieved.

Influence of ignition condition on the growth of silicon thin films using plasma enhanced chemical vapour deposition

The influences of the plasma ignition condition in plasma enhanced chemical vapour deposition （PECVD） on the interfaces and the microstructures of hydrogenated microcrystalline Si （μc-Si：H） thin films are investigated. The plasma ignition condition is modified by varying the ratio of Sill4 to H2 （RH）. For plasma ignited with a constant gas ratio, the time-resolved optical emission spectroscopy presents a low value of the emission intensity ratio of Ha to Sill＊ （Iuα//SiH＊） at the initial stage, which leads to a thick amorphous incubation layer. For the ignition condition with a profiling RH, the higher IHα/ISiH＊ values are realized. By optimizing the RN modulation, a uniform crystallinity along the growth direction and a denser αc-Si：H film can be obtained. However, an excessively high IRα/ISIH＊ may damage the interface properties, which is indicated by capacitance-voltage （C-V） measurements. Well controlling the ignition condition is critically important for the applications of Si thin films.

Structural evolution and optical characterization in argon diluted Si:H thin films obtained by plasma enhanced chemical vapor deposition

The structural evolution and optical characterization of hydrogenated silicon(Si:H) thin films obtained by conventional radio frequency(RF) plasma enhanced chemical vapor deposition(PECVD) through decomposition of silane diluted with argon were studied by X-ray diffractometry(XRD),Fourier transform infrared(FTIR) spectroscopy,Raman spectroscopy,transmission electron microscopy(TEM),and ultraviolet and visible(UV-vis) spectroscopy,respectively.The influence of argon dilution on the optical properties of the thin films was also studied.It is found that argon as dilution gas plays a significant role in the growth of nano-crystal grains and amorphous network in Si:H thin films.The structural evolution of the thin films with different argon dilution ratios is observed and it is suggested that argon plasma leads to the nanocrystallization in the thin films during the deposition process.The nanocrystallization initiating at a relatively low dilution ratio is also observed.With the increase of argon portion in the mixed precursor gases,nano-crystal grains in the thin films evolve regularly.The structural evolution is explained by a proposed model based on the energy exchange between the argon plasma constituted with Ar* and Ar+ radicals and the growth regions of the thin films.It is observed that both the absorption of UV-vis light and the optical gap decrease with the increase of dilution ratio.

Plasma-Enhanced Atomic Layer Deposition of Amorphous Ga_(2)O_(3) for Solar-Blind Photodetection

Wide-bandgap gallium oxide(Ga_(2)O_(3))is one of the most promising semiconductor materials for solar-blind(200 nm to 280 nm)photodetection.In its amorphous form,amorphous gallium oxide(a-Ga_(2)O_(3))maintains its intrinsic optoelectronic properties while can be prepared at a low growth temperature,thus it is compatible with Si integrated circuits(ICs)technology.Herein,the a-Ga_(2)O_(3) film is directly deposited on pre-fabricated Au interdigital electrodes by plasma enhanced atomic layer deposition(PE-ALD)at a growth temperature of 250°C.The stoichiometric a-Ga_(2)O_(3) thin film with a low defect density is achieved owing to the mild PE-ALD condition.As a result,the fabricated Au/a-Ga_(2)O_(3)/Au photodetector shows a fast time response,high responsivity,and excellent wavelength selectivity for solar-blind photodetection.Furthermore,an ultra-thin MgO layer is deposited by PE-ALD to passivate the Au/a-Ga_(2)O_(3)/Au interface,resulting in the responsivity of 788 A/W(under 254 nm at 10 V),a 250-nm-to-400-nm rejection ratio of 9.2×10^(3),and the rise time and the decay time of 32 ms and 6 ms,respectively.These results demonstrate that the a-Ga_(2)O_(3) film grown by PE-ALD is a promising candidate for high-performance solar-blind photodetection and potentially can be integrated with Si ICs for commercial production.

Influence of the Plasma State on the Formation of Nano Crystalline SiC Films

The influence of the plasma state on the microstructure transformation from amorphous to nano-(crystalline) state is emphasized during the formation of the silicon carbide (SiC) films deposited by the plasma enhanced chemical vapor technique. The effect of two key parameters, the working pressure and hydrogen concentration in the gas flow, that perform the dependence by modulating the two essential factors of the plasma state-ions energy and gas composition, is in-depth investigated. The experimental results showed that nanocrystalline SiC films fit for field emitters could be achieved under an appropriate ion energy flow density and gas components in the (plasma.)

Preparation of TiO2/MCM-41 by plasma enhanced chemical vapor deposition method and its photocatalytic activity

Titanium dioxide is coated on the surface of MCM-41 wafer through the plasma enhanced chemical vapor deposition （PECVD） method using titanium isopropoxide （TTIP） as a precursor. Annealing temperature is a key factor affecting crystal phase of titanium dioxide. It will transform an amorphous structure to a polycrystalline structure by increasing temperature. The optimum anatase phase of TiO2 which can acquire the best methanol conversion under UV-light irradiation is obtained under an annealing temperature of 700℃ for 2 h, substrate tem- perature of 500~C, 70 mL. min1 of oxygen flow rate, and 100W of plasma power. In addition, the films are composed of an anatase-rutile mixed phase, and the ratio of anatase to rutile varies with substrate temperature and oxygen flow rate. The particle sizes of titanium dioxide are between 30.3 nm and 59.9nm by the calculation of Scherrer equation. Under the reaction conditions of ll6.8mg.L-1 methanol, 2.9mg.L-1 moisture, and 75~C of reaction temperature, the best conversion of methanol with UV-light is 48.2% by using the anatase-rutile （91.3/ 8.7） mixed phase TiO2 in a batch reactor for 60 min. While under fluorescent light irradiation, the best photoactivity appears by using the anatase-rutile （55.4/44.6） mixed phase TiO2 with a conversion of 40.0%.

Synthesis and Characteristics of Fe_3C Nanoparticles Embedded in Amorphous Carbon Matrix

We proposed a new way to synthesize a nanocomposite consisted of cementite Fe3C nanoparticles and amorphous carbon by radio frequency plasma-enhanced chemical vapor deposition. Transmission electron microscope images show the existence of nanometric dark grains（Fe3C） embedded in a light matrix（amorphous carbon） in the samples. X-ray photoelectron spectroscopy experiment exhibit that the chemical bonding state in the films corresponded to sp3/sp2 amorphous carbon, sp^3 C-N（287.3 eV） and C15 in Fe3C（283.5 eV）. With increasing deposition time, the ratio of amorphous carbon increased. The magnetic measurements show that the value of in-lane coercivity increased with increasing carbon matrix concentration（from about 6.56× 10^3 A/m for film without carbon structures to approximately 2.77× 10^4 and 5.81 × 10^4 AJm for nanocomposite films at room temperature and 10 K, respectively）. The values of saturation magnetization for the synthesized nanocomposites were lower than that of the bulk Fe3C （ 140 Am^2/kg）.

Mechanical properties of AISI 1045 ceramic coated materials by nano indentation and crack opening displacement method

Abstract： An effective approach was conducted for estimating fracture toughness using the crack opening displacement （COD） method for plasma enhanced chemical vapor deposition （PECVD） coating materials. For this evaluation, an elastoplastic analysis was used to estimate critical COD values for single edge notched bending （SENB） specimens. The relationship between fracture toughness （Kic） and critical COD for SENB specimens was obtained. Microstructure of the interface between AleO3-TiO2 composite ceramic coatings and AISI 1045 steel substrates was studied by using scanning electron microscope （SEM）. Chemical compositions were clarified by energy-dispersive X-ray spectroscopy （EDS）. The results show that the interface between of Al203-TiO2 and substrate has mechanical combining. The nanohardness of the coatings can reach 1 200 GPa examined by nanoindentation. The Klc was calculated according to this relationship from critical COD. The bending process produces a significant relationship of COD independent of the axial force applied. Fractographic analysis was conducted to determine the crack length. From the physical analysis of nanoindentation curves, the elastic modulus of 1045/AI2O3-TiO2 is 180 GPa for the 50 μm film. The highest value of fracture toughness for 1045/A1203-TiO2-250 μm is 348 MPa·mv2.

Effect of ammonia gas etching on growth of vertically aligned carbon nanotubes/nanofibers

The etching effect of ammonia （NH3） on the growth of vertically aligned nanotubes/nanofibers （CNTs） was investigated by direct-current plasma enhanced chemical vapor deposition （DC-PECVD）. NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etching is different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth, the single strand CNT growth requires shorter etching time （5 min） than large catalytic patterns （10 rain） since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy （HTEM） shows fishbone structure of CNTs grown by PECVD.

A simple method to synthesize worm-like AlN nanowires and its field emission studies

The worm-like AlN nanowires are fabricated by the plasma-enhanced chemical vapor deposition(PECVD)on Si substrates through using Al powder and N2 as precursors,CaF2 as fluxing medium,Au as catalyst,respectively.The as-grown worm-like AlN nanowires each have a polycrystalline and hexagonal wurtzite structure.Their diameters are about 300 nm,and the lengths are over 10μm.The growth mechanism of worm-like AlN nanowires is discussed.Hydrogen plasma plays a very important role in forming the polycrystalline structure and rough surfaces of worm-like AlN nanowires.The worm-like AlN nanowires exhibit an excellent field-emission(FE)property with a low turn-on field of 4.5 V/μm at a current density of 0.01 mA/cm^(2) and low threshold field of 9.9 V/μm at 1 mA/cm^(2).The emission current densities of worm-like AlN nanowires each have a good stability.The enhanced FE properties of worm-like AlN nanowires may be due to their polycrystalline and rough structure with nanosize and high aspect ratio.The excellent FE properties of worm-like AlN nanowires can be explained by a grain boundary conduction mechanism.The results demonstrate that the worm-like AlN nanowires prepared by the proposed simple and the PECVD method possesses the potential applications in photoelectric and field-emission devices.

Influence of total gas flow rate on microcrystalline silicon films prepared by VHF-PECVD

Hydrogenated microcrystalline silicon （μc-Si：H） films are fabricated by very high frequency plasma enhanced chemical vapour deposition （VHF-PECVD） at a silane concentration of 7% and a varying total gas flow rate （H2＋SiH4）. Relations between the total gas flow rate and the electrical and structural properties as well as deposition rate of the films are studied. The results indicate that with the total gas flow rate increasing the photosensitivity and deposition rate increase, but the crystalline volume fraction （Xc） and dark conductivity decrease. And the intensity of （220） peak first increases then decreases with the increase of the total gas flow rate. The cause for the changes in the structure and deposition rate of the films with the total gas flow rate is investigated using optical emission spectroscopy （OES）.

Effect of Chamber Conditions and Substrate Type on PECVD of SiGeSn Films

In the past studies have shown that the addition of Ge and Sn into Si lattice to form SiGeSn enhances its carrier mobility and band-gap properties. Conventionally SiGeSn epitaxial films are grown using Ultra-High Vacuum (UHV) conditions with pressures ranging from 10-8 torr to 10-10 torr which makes high volume manufacturing very expensive. On the contrary, the use of low-pressure CVD processes (vacuum levels of 10-2 torr to 10-4 torr) is economically more viable and yields faster deposition of SiGeSn films. This study outlines the use of a cost-effective Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor to study the impact of substrate temperature and substrate type on the growth and properties of polycrystalline SiGeSn films. The onset of polycrystallinity in the films is attributed to the oxygen-rich PECVD chamber conditions explained using the Volmer-Weber (3D island) mechanism. The properties of the films were characterized using varied techniques to understand the impact of the substrate on film composition, thickness, crystallinity, and strain.

Surface plasmon-enhanced amorphous-silicon-nitride light emission with single-layer gold waveguides

Surface-plasmon （SP） enhancement of amorphous-silicon-nitride （a-SiNx） light emission with single-layer gold （Au） waveguides is experimentally demonstrated through time-resolved photoluminescence measure- ment. The a-SiN~ active layer with strong steady-state photoluminescence at 560 nm is prepared by plasma-enhanced chemical vapor deposition, and ricated by magnetron sputtering. The maximum the Au waveguide on the top of the a-SiNx layer is lab- Purcell factor value of -3 is achieved with identified SP resonance of the Au waveguide at -530 nm.

Dependence of wet etch rate on deposition,annealing conditions and etchants for PECVD silicon nitride film

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE

Direct growth of globally aligned graphene nanoribbons on reconstructed sapphire substrate using PECVD

Graphene nanoribbons(GNRs)are regarded as an ideal candidate for beyond-silicon electronics.However,synthesis of aligned GNR arrays on insulating substrates with high efficiency is challenging.In this work,we develop a facile strategy,involving KOH pre-treatment and high-temperature annealing,to construct parallel steps on the two-fold symmetry a-plane sapphire substrate.Horizontal GNRs as narrow as 15.1 nm with global alignment across a region of 20 mm^(2)are then grown on the step edgeenriched substrate through plasma enhanced chemical vapor deposition(PECVD)method.GNRs align well along the atomic steps on sapphire([■]direction)with their widths and densities swiftly adjustable by step morphology modification on substrate surface.A step-edge confined growth mechanism is proposed,attributing the constraint on the nanoribbon broadening to a relatively low growth temperature in PECVD,which restrains the activation energy to suppress GNRs across step edges on sapphire and prevents detrimental nanoribbon widening.The results provide a new perspective for scalable synthesizing well aligned nanoribbons of other two-dimensional materials.

Catalyst-Free Growth of Nanographene Films on Various Substrates

We have developed a new method to grow uniform graphene films directly on various substrates, such as insulators, semiconductors, and even metals, without using any catalyst. The growth was carried out using a remote plasma enhancement chemical vapor deposition （r-PECVD） system at relatively low temperatures, enabling the deposition of graphene films up to 4-inch wafer scale. Scanning tunneling microscopy （STM） confirmed that the films are made up of nanocrystalline graphene particles of tens of nanometers in lateral size. The growth mechanism for the nanographene is analogous to that for diamond grown by PECVD methods, in spite of sp2 carbon atoms being formed in the case of graphene rather than sp3 carbon atoms as in diamond. This growth approach is simple, low-cost, and scalable, and might have potential applications in fields such as thin film resistors, gas sensors, electrode materials, and transparent conductive films.

Laser annealing of SiO2 film deposited by ICPECVD for fabrication of silicon based low loss waveguide

Laser annealing of silicon dioxide （SiO2） film formed by inductively coupled plasma enhanced chemical vapor deposition （ICPECVD）is studied for the fabrication of low loss silicon based waveguide. The influence of laser annealing on ICPECVD-deposited SiO2 film is investigated. The surface roughness, refractive index, and etch rate of annealed samples are compared with those of SiO2 film obtained by thermal oxidation. It is demonstrated that the performance of ICPECVD-deposited SiO2 film can be significantly improved by laser annealing. Al2O3/SIO2 waveguide has been fabricated on silicon substrate with the SiO2 lower cladding formed by ICPECVD and laser annealing process, and its propagation loss is found to be comparable with that of the waveguide with thermally oxidized lower cladding.

Optical absorption enhancement of μc-SiGe:H films deposited via high pressure and high power

Hydrogenated microcrystalline silicon-germanium(μc-SiGe:H) films are fabricated by radio-frequency plasma-enhanced chemical vapor deposition(RF-PECVD).The optical absorption coefficient and the photosensitivity of the μc-SiGe:H films increase dramatically by increasing the plasma power and deposition pressure simultaneously.Additionally,the microstructural properties of the μc-SiGe:H films are also studied.By combining Raman,Fourier transform infrared(FTIR) and X-ray fluoroscopy(XRF) measurements,it is shown that the Ge-bonding configuration and compactability of the μc-SiGe:H thin films play a crucial role in enhancing the optical absorption and optimizing the quality of the films via a significant reduction in the defect density.

Fabrication of silica-on-silicon planar lightwave circuits by PECVD and ECR

Plasma enhanced chemical vapor deposition (PECVD) and electron cyclotron resonance (ECR) etching were used in the development of silica layers for planar waveguide applications. The addition of GeH4 to silica was used to control the refractive index of core layers with core-to-clad index differences in the range of 0.2%-1.3%. Refractive index uniformity variance of ±0.0003 was achieved after annealing for 4-inch Si (100) wafers. The core layers with thickness up to 6 μm were etched by ECR with optimized recipe and mask material. Low-loss silica-on-silicon waveguides whose propagation loss is approximately 0.07 dB/cm at 1550 nm are fabricated.

Investigation of high extraction efficiency flip-chip GaN-based light-emitting diodes

In order to obtain higher light output power, the flip-chip structure is used. We studied the ratio of the light of GaN sides before and after fabricating metal reflector on p-GaN. The SiO2/SiNx dielectric film reflectors were deposited through plasma enhance chemical vapor deposition following the fabrication of metal reflector, and then the dielectric film reflectors on the electrodes were etched in order to expose the electrodes to the air. It is found that comparing with the flip-chip GaN-LED without dielectric film reflectors, light output power can be increased by as high as 10.2% after the deposition of 2 pairs of SiO2/SiNx dielectric film reflectors on GaN-LEDs, which cover the sidewalls and the areas without the metal reflector. This result indicates that the high reflector formed by multi-layer dielectric films is useful to enhance the light output power of GaN-based LED, which reflects light from step sidewalls and p-GaN without metal reflector to internal, and then light emits from the surface.