Diamond-like Nanocomposite Thin Films Research Articles

Diamond-like nanocomposite: a novel promising carbon based thin film as antireflection and passivation coating for silicon solar cell

Presently, silicon nitride (SiNx) is widely used as antireflection coating (ARC) on p-type silicon solar cell. But, two highly toxic gasses ammonia and silane are used. In the present study, the ARC and passivation properties of diamond-like nanocomposite (DLN) thin film on silicon solar cell have been investigated. The DLN thin film has been deposited by rf-PACVD process using liquid precursor HMDSO in argon plasma. The film has been characterized by FESEM, HRTEM, FTIR, and Raman spectroscopy. The optical properties have been estimated by UV–vis–NIR spectroscopy. The minimum reflection has been achieved to 0.75% at 630 nm. Both the short circuit current density and open circuit voltage has been increased significantly from 28.6 mA cm−2 to 35.5 mA cm−2 and 0.551 V to 0.613 V respectively. The field effect passivation has been confirmed by dark IV characterization of c-Si /DLN heterojunction structure. All these lead to enhancement of efficiency by almost 4% absolute, which is comparable to SiNx. The ammonia and silane free deposited DLN thin film has a great potential to use as ARC for silicon based solar cell.

Effect of annealing on structural and optical properties of diamond-like nanocomposite thin films

The annealing effect on structural and optical properties of the Diamond-like Nanocomposite (DLN) thin film deposited on glass substrate by Plasma Assisted Chemical Vapor Deposition (PACVD) method has been investigated. The films were annealed at temperature ranging from 300 to 600 °C, with 100 °C interval for 9 minutes by rapid thermal process (RTP) under vacuum. The structural changes of the annealed films have been studied using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscope (SEM), and optical parameters have been determined using transmittance and reflectance spectra in UV-UIS-NIR range. The result shows that the refractive index increases gradually from 1.79 to 2.84 with annealing temperature due to out-diffusion of H by breaking Si–H and C–H bond leads to Si–C bond, i.e. more cross linking structure. In higher temperature range, graphitization also enhanced the refractive index. However, the optical band gap at up to 400 °C initially increases from 3.05 to 3.20 eV and then decreases due to graphitization. The film has a great potential to be used as anti-reflection coating (ARC) on silicon-based solar cell.

A Clue to Understand Environmental Influence on Friction and Wear of Diamond-Like Nanocomposite Thin Film

The wear and friction of diamond-like nanocomposite (DLN) film have been investigated in air with different relative humidity (RH), under deionized (DI) water and saline solution. The structure of the film has been characterized by Fourier transform infrared (FTIR), Raman spectroscopy, and scanning electron microscope (SEM). The result shows two interpenetrating network structure: a–C:H and a–Si:O, and they are interpenetrated by Si–C bonding. The tribological performance has been measured using ball-on-disc tribometer with tungsten carbide ball as counterbody at 10 N normal load. Results show that with increasing relative humidity (RH) from 35% to 80%, the coefficient of friction (COF) increases gradually from 0.005 to 0.074, whereas with increasing RH the wear factor decreases from9.8×10−8 mm3/Nm and attains a minimum value of2.7×10−8 mm3/Nm at 50% RH. With further increase of RH the wear factor increases again. Moreover, in DI water and especially in saline solution, both the COF and wear factor have been found to be significantly low. A clue has been interpreted to understand environmental dependency, considering the effect of surface dangling bonds, charge transfer, and chemical interactions.

Influence of flow rate on different properties of diamond-like nanocomposite thin films grown by PECVD

Diamond-like nanocomposite (DLN) thin films were deposited on pyrex glass substrate using different flow rate of haxamethyldisiloxane (HMDSO) based liquid precursor with nitrogen gas as a glow discharged decomposition by plasma enhanced chemical vapor deposition (PECVD) technique. The significant influence of different precursor flow rates on refractive index and thickness of the DLN films was measured by using spectroscopic filmatrics and DEKTAK profilometer. Optical transparency of the DLN thin films was analyzed by UV-VIS-NIR spectrometer. FTIR spectroscopy, provides the information about shifted bonds like SiC2, Si-C, Si-O, C-C, Si-H, C-H, N-H, and O-H with different precursor flow rate. We have estimated the hardness of the DLN films from Raman spectroscopy using Gaussian deconvolution method and tried to investigate the correlation between hardness, refractive index and thickness of the films with different precursor flow rates. The composition and surface morphology of the DLN films were investigated by X-ray photo electron spectroscopy (XPS) and atomic force microscopy (AFM) respectively. We have analyzed the hardness by intensity ratio (ID/IG) of D and G peaks and correlates with hardness measurement by nanoindentation test where hardness increases from 27.8 μl/min to 80.6μl/min and then decreases with increase of flow rate from 80.6μl/min to 149.5μl/min. Finally, we correlates different parameters of structural, optical and tribological properties like film-thickness, refractive index, light transmission, hardness, surface roughness, modulus of elasticity, contact angle etc. with different precursor flow rates of DLN films.

Frequency response of Diamond-like Nanocomposite thin film based MIM capacitor and equivalent circuit modelling

The frequency response of metal-insulator-metal (MI M) based thin film capacitors were studied using LCR bridge where diamond-like nanocomposite ( DLN) film behaves as a dielectric medium. The films were deposited by plasma assisted chemical vapour d eposition (PACVD) method. Fourier transforms infrar ed spectroscopy (FTIR) and Raman spectroscopy give the structure of DLN film. The results show that, equi valent parallel capacitance (EPC) decreases sharply beyond 10 5 Hz for thinner films. But for thicker films, there is no such decrease. This is due to some parasitic series resistance effect in the capacitor circuit. An equ ivalent circuit model for real capacitor has been establish ed. Moreover, there is also a small decrement in EP C with frequency and this effect increases with thickness of film. This may be due to lack of sufficient time for electron transportation through bulk DLN material. The DLN b ased thin film capacitor has a great potential for use in electronic/electrical system.

Structural and tribological properties of diamond-like nanocomposite thin films

The structural and tribological properties of diamond-like nanocomposite (DLN) thin films, deposited by radio frequency plasma enhanced chemical vapor deposition (rf-PECVD) on the pyrex glass or silicon substrate using the combinations of siloxane and silazane based gas precursors, are discussed. High resolution transmission electron microscopy (HRTEM) result shows the DLN film structure with different nanoparticle size. The surface morphology of the DLN films has been investigated by using atomic force microscopy (AFM). The structural properties of the DLN films are analyzed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We have observed different bonds like C―C, C―H, C―Si, C―O, Si―O, Si―H, etc. in the DLN films by XPS and FTIR analysis, which reveal that it consists of a-C:H and a-Si:O networks. The disorder and graphitic structure of amorphous carbon of the deposited films are analyzed by Raman spectroscopy. The hardness and friction coefficient of the films are measured by nanoindentation and scratch test techniques. Finally, we find that mixed siloxane and silazane precursor (MSSP) based DLN films provide better film-properties like surface roughness, friction coefficient, etc. than those of single siloxane or silazane precursor (SSSP) based DLN films.

Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of CC, CH, SiC, and SiH bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio ID/IG. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

Compatibility Study of Diamond-Like Nanocomposite Thin Films with Hydrazine Propellant for MEMS Microthruster

In this paper, the etching characteristic of diamond like nanocomposite thin films materials in hydrazine has been reported. The experiments have been carried out to explore the compatibility of hydrazine as a propellant with silicon based microthruster. In the reported work, 2″ N-type (100) silicon wafer with 4-6 Ω cm resistivity were used as base material. Diamond-like nanocomposite (DLN) films are deposited on silicon substrate by plasma enhanced chemical vapor deposition (PECVD) process using siloxane or silazane based precursors or their combinations. Thickness of deposited DLN thin films is around 1 µm. DLN samples are treated in 98% hydrazine at 25 °C, 70 °C and 90 °C for different time and etch rates and subsequently the change in refractive index of the DLN films if any has been measured.

Biocompatibility of diamond-like nanocomposite thin films

Diamond-like nanocomposite (DLN) films consist of network structure of amorphous carbon and quartz like silicon. In the present work, DLN films have been synthesized on pyrex glass and subsequently, their biocompatibility have been investigated through primary and secondary cell adhesion, cytotoxicity, protein adsorption and murine peritoneal macrophage activation experiments. Variable degree of cell and protein response have been found based on variable film synthesis parameters but in overall, required biocompatibility has been established for all types of film-coating.