Hot Filament Chemical Vapor Deposition Research Articles

The effect of laser texture on adhesion and tribological properties of boron-doped diamond film on WC-Co cemented carbide

The mismatch between the coefficients of thermal expansion of diamond and WC-Co cemented carbide causes hot filament chemical vapor deposition 1 1 HFCVD (HFCVD) diamond film tools to be prone to film flaking and wear, which severely limits their promotion in the field of ultra-precision machining. The aim of this paper is to investigate the effect of different texture on the adhesion and friction properties of boron-doped diamond 2 2 BD (BD) film. Processing of different types and depth-diameter ratio of textures on carbide surfaces by laser technology and deposition of BD films by HFCVD method. The microstructure of films was characterized, the adhesion strength and friction properties of films were study by indentation and friction tests. The results show that texture with 15 % depth-diameter ratio facilitates the growth of diamond in (111) crystal face orientation and inhibits the production of non-diamond carbon in the sp2 structure, and the secondary nucleation rate of diamond in texture edge is higher. The compressive stress at the edge of the texture with 15 % depth-diameter ratio is greater, resulting in stronger adhesion of the film. Under dry friction environment, serrated texture has a lower coefficient of friction and wear rate than grooved texture due to its excellent chip storage capacity. However, the depth-diameter ratio should not be too large, grooved texture with 30 % depth-diameter ratio will reduce the friction performance and adhesion of BD film. Therefore, the adhesion and tribological properties of BD film can be improved by changing the texture type and the depth-diameter ratio, of which the effect of the depth-diameter ratio is more significant. • Secondary nucleation rate is higher at the texture edge. • Higher compressive residual stress and adhesion at the edge of texture • Texture depth-diameter ratio has great influence on the properties of diamond film. • The prepared tools show the common advantages of combining textured and film tools.

Structural characteristics and gas sensing response of V2O5 nanorod thinfilms deposited by hot filament CVD

Using the novel hot filament chemical vapor deposition (HFCVD) technique, thinfilms of vanadium pentoxide (V2O5) were deposited under various conditions. The structural characteristics and gas sensing response of the thinfilms were investigated. X-ray diffraction shows that the thinfilms are orthorhombic V2O5 with (001) preferred orientation. Scanning electron microscopy observation reveals that nanorod thinfilms could be obtained under optimized oxygen content and substrate to filament distance. The sensing response of the nanorod thinfilm towards ammonia and ethanol were tested. It exhibits a sensing response of 1.557 and 1.721 towards 200 ppm ammonia and ethanol, respectively, with a response time of 14 s and 20 s after the exposure to ethanol and ammonia and a corresponding recovery time of 26 s and 38 s respectively.

Multi-Frequency Light Sources Based on CVD Diamond Matrices with a Mix of SiV- and GeV- Color Centers and Tungsten Complexes.

Recently, nanodiamonds with negatively charged luminescent color centers based on atoms of the fourth group (SiV-, GeV-) have been proposed for use as biocompatible luminescent markers. Further improvement of the functionality of such systems by expanding the frequencies of the emission can be achieved by the additional formation of luminescent tungsten complexes in the diamond matrix. This paper reports the creation of diamond matrices by a hot filament chemical vapor deposition method, containing combinations of luminescing Si-V and Ge-V color centers and tungsten complexes. The possibility is demonstrated of creating a multicolor light source combining the luminescence of all embedded emitters. The emission properties of tungsten complexes and Si-V and Ge-V color centers in the diamond matrices were investigated, as well as differences in their luminescent properties and electron-phonon interaction at different temperatures.

Measurement and calibration of substrate surface temperature in hot filament chemical vapor deposition

The temperature measurement under complex working conditions has always been a challenging task. In this study, taking the hot filament chemical vapor deposition (HFCVD) as an example, the method of measuring the surface temperature of cemented carbide inserts was explored by using K-type thermocouples for contact measurement. Several different thermocouple installation schemes were designed, and an established evaluation system was used as a standard to identify the feasibility of these schemes, including measurement stability, calibration stability, convenience of installation, and cost performance. Finally, the optimal scheme was screened, that is, to insert the temperature measurement segment of a thermocouple into the central through hole of the substrate and keep the tip flush with the surface. It not only protected the thermocouple from being deteriorated by the high temperature gradient field, but also ensured that the thermocouple could sense the heat change that is consistent with the measured substrate surface, improving the stability of the measurement. Noted was that a calibration value should be added to the thermocouple indication value in order to obtain the accurate surface temperature, and thus the measurement and calibrated standard deviations could be controlled as less than 15 °C and 10.81 °C, respectively. The optimal measurement scheme was applied to the actual deposition experiments of diamond films, and the dependence of the coating quality on the temperature was analyzed, which further verified the accuracy of the temperature measurement. This scheme can be extended to other similar complex conditions, including vacuum, large temperature gradient, severe mutual occlusion between objects, or strong chemical reactions.

Deposition of an adherent diamond film on stainless steel using Cr/Cr[sbnd]Al[sbnd]N as an interlayer

Cr/CrAlN films were chosen as an interlayer to deposit an adherent diamond film on stainless steels by using hot filament chemical vapor deposition (HFCVD). The results show that diamond film with good adhesion is successfully deposited on 3Cr13 stainless steel when the interlayer with Al content from 0 to 18 at.%, which is ascribed to high chemical adhesion by a certain amount of chromium carbide. When Al content in the interlayer further increases, an excessive Al2O3 is formed on the surface of the interlayer, carbon supersaturation is easily arrived, so that the amount of the carbide at the diamond/interlayer interface decreases evidently. This decreases the strength of the covalent bonding from the carbide, producing poor adhesion. Moreover, with the raise of Al content in the interlayer, the hardness of the multilayer coated stainless steel increases due to the increase of the interlayer's hardness and the slight increase of the diamond content in the film.

Bottom-up evolution of consolidated porous diamond layer by hot-filament-CVD

Synthesis of the porous chemical vapor deposition (CVD) diamond layer, which might enable many noble applications, usually employed the template growth or post-processing, which accompanied the undesirable complexity and cost issues. In a small number of the porous diamond layer synthesis efforts, majority of them employed the plasma-assisted CVD (PA-CVD), while the hot-filament CVD (HF-CVD) was well known for its outstanding scalability and cost-effectiveness. Here we demonstrate a post-processing/template-free approach for the porous diamond layer synthesis by HF-CVD. Intriguingly, we found that the seeding the substrate by detonation nanodiamond (DND) and the relatively low substrate temperature were key enabling factors. The consolidated layer was consisted of quasi-spherical nanodiamond particles. Such observations suggested a precipitation-relevant growth mechanism, which we disproved here, and we clarified an alternative bottom-up growth mechanism. We also demonstrated a preliminary result of applying the porous diamond layer as a waveguide in the attenuated-total-reflection (ATR)-type waveguide mode resonance sensor.

Viability and proliferation of A549 cell line on the surface of micro-, nano- and ultrananocrystalline diamond films grown by HFCVD with tailored gases

This article describes key material science/technology issues to implement polycrystalline diamond scaffolds to enable processes for biological cells growth relevant for using cells grown in the laboratory for the treatment of human biological conditions. Issues investigated include 1. Synthesis/characterization of microcrystalline diamond (MCD), nanocrystalline diamond (NCD) and transformational ultrananocrystalline diamond (UNCD) coating-based scaffolds. Diamond films were grown on silicon substrates using the hot filament chemical vapor deposition (HFCVD) technique, by which filaments heated to ∼2,300 °C induce cracking of CH4 molecules into C atoms/CHx (x = 1, 2, 3) radicals, growing diamond films via chemical reaction on the substrates’ surface. MCD and NCD + films were grown flowing the H2/CH4 gas mixture. NCD- and UNCD films were grown using the Ar/CH4 gas mixture plus H2 flux (73.5%, 49%, and 9.8%), which for high fluxes, induced increased the concentration of H-containing trans-polyacetylene (T-PA) molecules in UNCD films’ grain boundaries, impacting biological performance. 2. Studies of viability and proliferation of human lung carcinoma cell line (A549) grown on surfaces of MCD, NCD, and UNCD films, using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, which showed no significant difference in cell proliferation among the MCD, NCD, and UNCD films.

Mechanical properties evaluation of diamond films via nanoindentation

Diamond film is considered ideal tool coating material for processing difficult-to-machine materials due to the high hardness and wear resistance. However, precisely evaluating the mechanical properties of diamond films has been a considerable obstacle, which hinders further design and application. In this work, various diamond films were deposited on cemented carbide substrates ranging from 0.1 to 1.0 kPa in CH4/H2 by hot filament chemical vapor deposition. The mechanical properties of diamond films were systematically and rigorously evaluated by nanoindentation adopting a series of loads. However, it is found that hardness calculated at different loads has a significant deviation, although all obey the well-known 10 % rule of thumb. On basis of the massive nanoindentation on polished diamond film with roughness <20 nm, we propose a stricter 5 %, instead of the well-known 10 % rule of thumb, for the limit of maximum penetration depth divided by film thickness in the diamond nanoindentation measurements. Notably, the mechanical properties of the deposited diamond films improved as the pressure increased, especially hardness gradually increased from 75.5 ± 1.4 GPa to 87.3 ± 5.0 GPa, which is attributed to the increase of the ratio of sp3 carbon content.

Graphene Film Growth on Silicon Carbide by Hot Filament Chemical Vapor Deposition

The electrical properties of graphene on dielectric substrates, such as silicon carbide (SiC), have received much attention due to their interesting applications. This work presents a method to grow graphene on a 6H-SiC substrate at a pressure of 35 Torr by using the hot filament chemical vapor deposition (HFCVD) technique. The graphene deposition was conducted in an atmosphere of methane and hydrogen at a temperature of 950 °C. The graphene films were analyzed using Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray, and X-ray photoelectron spectroscopy. Raman mapping and AFM measurements indicated that few-layer and multilayer graphene were deposited from the external carbon source depending on the growth parameter conditions. The compositional analysis confirmed the presence of graphene deposition on SiC substrates and the absence of any metal involved in the growth process.

Growth of Nitrogen Incorporated Ultrananocrystalline Diamond Coating on Graphite by Hot Filament Chemical Vapor Deposition.

This article shows the results of experiments to grow Nitrogen incorporated ultrananocrystalline diamond (N-UNCD) films on commercial natural graphite (NG)/Cu anodes by hot chemical vapor deposition (HFCVD) using a gas mixture of Ar/CH4/N2/H2. The experiments focused on studying the effect of the pressure in the HFCVD chamber, filament-substrate distance, and temperature of the substrate. It was found that a substrate distance of 3.0 cm and a substrate temperature of 575 C were optimal to grow N-UNCD film on the graphite surface as determined by Raman spectroscopy, SEM, and TEM imaging. XPS analysis shows N incorporation through the film. Subsequently, the substrate surface temperature was increased using a heater, while keeping the substrate-filament distance constant at 3.0 cm. In this case, Raman spectra and SEM images of the substrate surface showed a major composition of graphite in the film as the substrate-surface temperature increased. Finally, the process pressure was increased to 10 Torr where it was seen that the growth of N-UNCD film occurred at 2.0 cm at a substrate temperature of 675 C. These results suggest that as the process pressure increases a smaller substrate-filament distance and consequently a higher substrate surface temperature can still enable the N-UNCD film growth by HFCVD. This effect is explained by a mean free path analysis of the main precursors H2 and CH3 molecules traveling from the filament to the surface of the substrate The potential impact of the process developed to grow electrically conductive N-UNCD films using the relatively low-cost HFCVD process is that this process can be used to grow N-UNCD films on commercial NG/Cu anodes for Li-ion batteries (LIBs), to enable longer stable capacity energy vs. charge/discharge cycles.

Construction of flexible fiber-shaped boron-doped diamond film and its supercapacitor application

Flexible fiber-shaped supercapacitors (FSSCs) are promising candidates as electrode materials for the development of deformable electronic devices. Although tremendous efforts have been focused on the preparation of flexible electrode materials, traditional FSSCs materials face problems of inferior stability and complicated processes. Boron-doped diamond (BDD) holds promise as a FSSC electrode, owing to its well-established preparation process, strong acid and alkali corrosion resistance, environmentally and skin-friendly characteristics. Here, we reported a novel strategy for the construction of BDD-based FSSCs by growing a BDD film on a flexible tantalum (Ta) fiber substrate through hot filament chemical vapor deposition technique. Results showed that the BDD fiber film featured 10 folds improvement in specific capacitance than a planar BDD electrode. A symmetric supercapacitor device was assembled using the BDD fiber electrode and achieved an energy density of 25.6 mJ cm−2 at a power density of 0.6 mW cm−2, and a desirable stability with higher capacitance retention of 93.5% after 20,000 cycles. Furthermore, the symmetric BDD fiber device exhibited satisfactory bendability with high specific capacitance retention under various bending deformations. The findings in this research work hold promise for the fabrication of high performance flexible FSSCs.

Numerical calculation of temperature, velocity, and species concentration distributions in a hot filament chemical vapor deposition in a reactor using a CH4/H2 mixture

This study is a numerical modeling of transport phenomena occurring in the reaction chamber during diamond or amorphous hydrogenated carbon films growth by a hot filament chemical vapor deposition (HFCVD) technique. A two-dimensional model was adopted to study the HFCVD reactor. The equations of heat, momentum, and mass transfer were solved numerically; the simulation was performed using a program in FORTRAN language. All temperature, velocity, and species concentration distributions were similar at the filaments and they were also similar between the filaments. The results show that the gas temperature increases when the number of filaments increases from three to four filaments. We also noted an increase in the production of CH3 and C2H5 radicals near the surface; there was also an increase in the growth rate of the thin film. The concentrations of C2H6, C2H4, and C2H5 were very high. Temperature and concentrations were affected by the distance between filaments and the distance filaments-substrates.

A nanoporous diamond particle microelectrode and its surface modification

Boron doped diamond electrode (BDDE) with dimensions of tens of or hundreds of μm has received widespread attention for electrochemical and biological applications because of exceptional features such as wide potential window for water stability, excellent electrochemical/chemical stability, and superior antifouling properties. This work reported a feasible way to fabricate a single nanoporous BDD particle microelectrode (sDPME) using a commercial single-crystal BDD particle (cBDD) as the substrate. The nanoporous surface of cBDD (pcBDD) was formed via thermal catalytic treatment with nickel as the catalyst, followed by further electrodeposition of gold nanoparticles (Au NPs) to fill the nanopores, increasing its electrocatalytic performance. As a comparison, the heavily-doped polycrystalline BDD film was deposited on cBDD via hot-filament chemical vapor deposition, increasing its electrical surface conductivity, followed by the similar thermal etching to form the nanoporous surface (prBDD) as well as Au NPs modification. We gradually characterized surface modification of cBDD using scanning electron microscopy, Raman, energy dispersive spectroscopy and various electrochemical techniques. The results demonstrated that among six sDPMEs, the Au NPs-modified nanoporous sDPMEs (Au/prBDD) have one order of magnitude higher heterogeneous electron transfer kinetic constant than the cBDD. This difference was attributed to synergistic effects of the improved electrical conductivity (with a higher doping level of few 1020 cm−3 versus 1018 cm−3), the improved capability for electron transfer (with lower charge transfer resistance of 1.3 kΩ versus 8.6 kΩ) as well as the increased electrochemically active surface area (1.12 mm2 versus 0.34 mm2).

Smart wear sensor device based on nanodiamond multilayers

Diamond coated cobalt-cemented tungsten carbide (WC-Co) cutting tools are widely used for machining light-weight engineering parts made of composite materials. Despite the existence of several methods that can monitor the cutting tools' failure, an earlier prediction only about the coating's wear situation before substrate damage is still missing. In this study, the development of a wear sensor prototype based on a nanocrystalline diamond multilayer system is presented. This multilayer system is built up by two conductive nanocrystalline diamond (CNCD) layers and one non-conductive nanocrystalline diamond (NCD) layer in between. Hot-filament chemical vapor deposition (HFCVD) was utilized as coating process for coating the multilayer system onto WC-Co dummy tools, using a gas mixture of methane and hydrogen. The CNCD's specific conductivity is 10 S/cm, whereas NCD's specific conductivity is 5.4 × 10 −6 S/cm. The impedances of the prototype in the as-grown state and after some wear losses were measured. A linear response of the impedance to the multilayer's wear situation was detected. A theoretical model was established for simulating the sensor principle qualitatively and calculating its sensitivity quantitatively. • A grain boundary dominated electrical conductivity at room temperature was found in undoped nanocrystalline diamond, using Hot-filament CVD for film deposition; • Multilayer sensor system prototype was built up with conductive and non-conductive diamond film layers onto cobalt-cemented tungsten carbide (WC-Co) cutting tools; • A theoretical model and an appropriate detection principle measuring impedance of multilayer's as-grown and wear losses situation were successfully achieved; • The wear situation of a cutting tool can be monitored during machining operation, as to realise an efficient protection of the cutting tools' basic body for possible further reusage.

Effects of Coating Parameters of Hot Filament Chemical Vapour Deposition on Tool Wear in Micro-Drilling of High-Frequency Printed Circuit Board

High-frequency and high-speed printed circuit boards (PCBs) are made of ceramic particles and anisotropic fibres, which are difficult to machine. In most cases, severe tool wear occurs when drilling high-frequency PCBs. To protect the substrate of the drills, diamond films are typically fabricated on the drills using hot filament chemical vapour deposition (HFCVD). This study investigates the coating characteristics of drills with respect to different HFCVD processing parameters and the coating characteristics following wear from machining high-frequency PCBs. The results show that the methane concentration, processing time and temperature all have a significant effect on the grain size and coating thickness of the diamond film. The grain size of the film obviously decreases as does the methane concentration, while the coating thickness increases. By drilling high-frequency PCBs with drills with nanocrystalline and microcrystalline grain sizes, it is discovered that drills with nanocrystalline films have a longer tool life than drills with microcrystalline films. The maximum length of the flank wear of the nanocrystalline diamond-coated drill is nearly 90% less than microcrystalline diamond-coated tools. Moreover, drills with thinner films wear at a faster rate than drills with thicker films. The findings highlight the effects of HFCVD parameters for coated drills that process high-frequency PCBs, thereby contributing to the production of high quality PCBs for industry and academia.

Preferentially oriented growth of diamond films on silicon with nickel interlayer

A multistep deposition technique is developed to produce highly oriented diamond films by hot filament chemical vapor deposition (HFCVD) on Si (111) substrates. The orientation is produced by use of a thin, 5–20 nm, Ni interlayer. Annealing studies demonstrate diffusion of Ni into Si to form nickel silicides with crystal structure depending on temperature. The HFCVD diamond film with Ni interlayer results in reduced non-diamond carbon, low surface roughness, high diamond crystal quality, and increased texturing relative to growth on bare silicon wafers. X-ray diffraction results show that the diamond film grown with 10 nm Ni interlayer yielded 92.5% of the diamond grains oriented along the (110) crystal planes with ~ 2.5 µm thickness and large average grain size ~ 1.45 µm based on scanning electron microscopy. Texture is also observed to develop for ~ 300 nm thick diamond films with ~ 89.0% of the grains oriented along the (110) crystal plane direction. These results are significantly better than diamond grown on Si (111) without Ni layer with the same HFCVD conditions. The oriented growth of diamond film on Ni interlayers is explained by a proposed model wherein the nano-diamond seeds becoming oriented relative to the β1-Ni3Si that forms during the diamond nucleation period. The model also explains the silicidation and diamond growth processes.Article HighlightsHigh quality diamond film with minimum surface roughness and ~93% oriented grains along (110) crystallographic direction is grown on Si substrate using a thin 5 to 20 nm nickel layer.A detailed report on the formation of different phases of nickel silicide, its stability with different temperature, and its role for diamond film texturing at HFCVD growth condition is presented.A diamond growth model on Si substrate with Ni interlayer to grow high quality-oriented diamond film is established.

Periodic porous 3D boron-doped diamond electrode for enhanced perfluorooctanoic acid degradation

Using diamond anodes for electrochemical removal of recalcitrant perfluorooctanoic acid (PFOA) pollutants has become an important strategy in recent research. However, the electrolysis removal efficiency of PFOA is still plagued by low electrochemical active surface area (EASA) and mass transfer limitation of conventional flat-plate diamond anodes. Herein, the periodic porous boron-doped diamond (PP-BDD) anodes were successfully prepared by 3D printing combined with hot-filament chemical vapor deposition (HF-CVD) technologies. The prepared PP-BDD anode achieves a higher PFOA kinetics (kapp = 0.022 min−1, the normalized rate constant is 6.6 m s−1) compared with the conventional 2D-BDD anode (kapp = 0.006 min−1, the normalized rate constant is 1.8 m s−1) at the applied density of 20 mA cm−2. The calculated mass transfer coefficient km of PFOA towards PP-BDD (2.6 × 10−5 m s−1) is about 6.1 times higher than that of 2D-BDD (0.42 × 10−5 m s−1), and the electron paramagnetic resonance (EPR) measurement verifies that PP-BDD produces more •OH and SO4•− radicals during the electrolysis process versus 2D-BDD. The unique periodic pore structure enables PP-BDD higher EASA than 2D-BDD and increases the mass transfer efficiency. Consequently, the number of electrolyte and PFOA molecule accessible diamond anode surface is increased. This work provides valuable guidance for the deterministic design of periodic pore structure-based BDD electrodes for efficient electrochemical oxidation (EO) of refractory pollutants.

Utilization of catalytically active metals in mining waste and water for synthesis of carbon nanotubes

This study presents the application of fine-grained precipitates from mine waters for the synthesis of carbon nanotubes. Experimental synthesis of carbon nanotubes was carried out on natural substrates taken from the Slovak mining localities Markušovce, Smolník and Poproč. The substrates were obtained from mining waste taken from the shore dark sediment settling ponds in Markušovce, from the water flowing out of the mine in Smolník and from the sediment collected from the mine of Poproč. The main components of the colloidal residues resulting from the extraction of ores are particles containing catalytically active metals. Microscopic analysis of nanocomposites synthetized in a hot filament chemical vapour deposition reactor shows that the sediments from all residues after ore mining have a high ability to catalyse the synthesis of carbon nanotubes. The combination of catalyst particles and co-catalyst plays an essential role in the formation of carbon nanotubes. • Precipitates from mining waste and water were used for catalyst preparation. • Colloidal residues are particles containing catalytically active metals. • Catalytically active metals are used for synthesis of carbon nanotubes and for nanocomposite formation by CVD technique. • Combination of catalyst particles and co-catalyst plays an essential role in the formation of carbon nanotubes and nanofibers.

Temperature-dependent residual stress and thermal stability studies of multilayer HF-CVD diamond coatings on RB-SiC

Structurally graded multilayer (ML) diamond coatings were deposited on reaction bonded silicon carbide (RB-SiC) using a hot filament chemical vapour deposition (HF-CVD) system via two different routes: a continuous process (C-ML) and a three-step intermittent process (Ix-ML, x being the number of steps). In this study, the temperature-dependent residual stresses and thermal stabilities of the C-ML and Ix-ML coatings after annealing at 100° intervals from 100 °C–800 °C were investigated. Scanning electron microscopy, 2D/3D Raman mapping, cluster analysis, and sp2/sp3 ratio computations were carried out at all stages and the results were compared. The residual stresses of the as-deposited coatings, I1-ML, I2-ML, I3-ML, and C-ML, were compressive with values of −1.09 GPa, −0.90 GPa, −0.62 GPa and −1.35 GPa, respectively, which progressively shifted to the tensile regime on annealing and exhibited values of 0.50 GPa, 0.50 GPa, 0.61 GPa and 1.75 GPa respectively, after annealing at 700 °C. The sp2/sp3 ratios of the C-ML and I3-ML coatings dropped from 0.94% to 0.54% and 1.07% to 0.54%, respectively, as the annealing temperature increased from 100 °C to 700 °C. All coatings were completely oxidised at 800 °C except I3-ML, where patches of the original coating persisted even after annealing at 800 °C.

MIS-Like Structures with Silicon-Rich Oxide Films Obtained by HFCVD: Their Response as Photodetectors.

MIS-type structures composed of silicon-rich oxide (SRO), thin films deposited by hot filament chemical vapor deposition (HFCVD), show interesting I-V and I-t properties under white light illumination and a response as photodetectors. From electrical measurements, it was found that at a reverse bias of −4 V, the illumination current increased by up to three orders of magnitude relative to the dark current, which was about 82 nA, while the photogenerated current reached a value of 25 μA. The reported MIS structure with SRO as the dielectric layer exhibited a hopping conduction mechanism, and an ohmic conduction mechanism was found with low voltage. I-t measurements confirmed the increased photogenerated current. Furthermore, the MIS structure, characterized by current-wavelength (I-λ) measurements, exhibited a maximum responsivity value at 254 mA/W, specific detectivity (D*) at 2.21 × 1011 cm Hz1/2 W−1, and a noise equivalent power (NEP) of 49 pW at a wavelength of 535 nm. The structure exhibited good switching behavior, with rise and fall times between 120 and 150 ms, respectively. These rise and decay times explain the generation and recombination of charge carriers and the trapping and release of traps, respectively. These results make MIS-type structures useful as photodetectors in the 420 to 590 nm range.