K. Dayana

Surface Morphology and Compositional Analysis of Undoped Amorphous Carbon Thin Films via Bias Assisted Pyrolysis-CVD

Amorphous carbon (a:C) were successfully deposited on the silicon surfaces via bias assisted pyrolysis-CVD in the range between 350oC to 500oC with constant of negative bias -50V in 1 hour deposition. The heated of palm oil at about 150oC was vaporized then used for deposited onto p-type silicon substrates. The deposited thin films were characterized by using field emission scanning electron microscopic (FESEM), energy dispersive analyser x-ray (EDAX). We have found carbon element at about 0.15 keV from EDAX with surface morphology formed a nano-ball like structure at 450oC of palm oil precursor. These results indicated deformation of physical and structural thin films caused by applied negative bias and the temperature.

New Method of Depositing the Nanostructured Amorphous Carbon for Carbon Based Solar Cell Applications

Nanostructured amorphous carbon (a-C) solar cells were successfully deposited via a self-designed aerosol-assisted chemical vapor deposition (AACVD). The fabricated solar cell with the configuration of Au/p-C/n-Si/Au achieved efficiency () of % for device deposited at 500°C, % for 450°C, and % for 400°C. Photoresponse characteristic was highlighted under illumination (AM 1.5 illuminations: 100 mW/cm2, 25°C), where conductivity increased when the sample was being hit by light. Transmittance spectrum exhibits a large transmittance value (85%) and absorption coefficient value of  cm−1 at the visible range from 390 to 790 nm. The nanostructured a-C thin film deposited at higher temperature possesses lower transmittance due to higher absorption as a result of the higher content of sp2-bonded carbon atoms. From Tauc’s plot, optical band gap () was determined, and decreased as deposition temperature increased (1.2 eV, 1.0 eV, 0.7 eV). On the other hand, FESEM images exhibited a nanostructured sized a-C with the particle size less than 100 nm. To the best of our knowledge, the presence of nanostructured particle of a-C by a self-prepared AACVD has not frequently been reported.

Iodine Doping of Amorphous Carbon Thin Films Deposited by Thermal CVD

A simple thermal chemical vapor deposition method is employed for the deposition of amorphous carbon thin films by natural precursor camphor oil onto the glass substrates and the iodine doping process. In this work, we have studied the effect of iodine doping on the evolution of electrical properties and the optical and structural properties of amorphous carbon thin films. The amorphous carbon thin films were characterized by using Raman spectroscopy, UV-VIS-NIR spectroscopy, current-voltage (I-V) measurement, Fourier transform infrared (FTIR) and FESEM. The I-V study reveals that the electrical conductivity was increased with the iodine doping. The iodine doped thin films induced graphitization by decreasing the optical band gap. Raman and FTIR result indicates that amorphous carbon thin films consist of a mixture of sp2 and sp3 bonded carbon atoms. The FESEM shows the amorphous nature of the thin films.

Raman spectra boron doped amorphous carbon thin film deposited by bias assisted-CVD

Boron doped amorphous carbon thin film carbon was deposited at 200°C-350°C by bias assisted-CVD using palm oil as a precursor material. The structural boron doped amorphous carbon films were discussed by Raman analysis through the evolution of D and G bands. The spectral evolution observed showed the increase of upward shift of D and G peaks as substrate deposition temperatures increased. These structural changes were further correlated with optical gap and the results obtained are discussed and compared. The estimated optical band gap is found to be 1.9 to 2.05 eV and conductivity is to be in the range of 10−5 Scm−1 to 10−4 Scm−1. The decrease of optical band gap is associated to conductivity increased which change the characteristic parameters of Raman spectra including the position of G peak, full width at half maximum of G peak, and ID/IG.Boron doped amorphous carbon thin film carbon was deposited at 200°C-350°C by bias assisted-CVD using palm oil as a precursor material. The structural boron doped amorphous carbon films were discussed by Raman analysis through the evolution of D and G bands. The spectral evolution observed showed the increase of upward shift of D and G peaks as substrate deposition temperatures increased. These structural changes were further correlated with optical gap and the results obtained are discussed and compared. The estimated optical band gap is found to be 1.9 to 2.05 eV and conductivity is to be in the range of 10−5 Scm−1 to 10−4 Scm−1. The decrease of optical band gap is associated to conductivity increased which change the characteristic parameters of Raman spectra including the position of G peak, full width at half maximum of G peak, and ID/IG.

Fabrication of a-C:B/n-Si Solar Cells with Low Positive Bias by Using Palm Oil Precursor

Boron doped amorphous carbon (a-C:B) film for heterojunction carbon-based photovoltaic solar cells were successfully fabricated on n-type silicon using palm oil precursor by the influenced of low positive bias voltage in the range of 0–50 V. The rectifying curve were found for all samples under dark measurement revealed that those samples were p-type semiconductor. The +30 V was found the optimized of the electronic properties with the open circuit voltage, current density, fill factor and efficiency were approximately 0.259034 V, 1.299456 mA/cm2, 0.240011 and 0.080788 %, respectively. The conversion efficiency of a-C:B has been improved under the influenced of low positive bias.

Properties of Iodine Doped Amorphous Carbon Thin Films Grown by Thermal CVD

Thin film of undoped and doped amorphous carbon has been achieved using the simple thermal CVD system in an ambient gas of Ar and Ar with I2, respectively. The electrical and optical properties of the iodine doped amorphous carbon (a-C:I) thin films were studied. The incorporation of iodine into the amorphous carbon thin film results in increase of electrical conductivity as doping temperature increase up to 400°C, which indicates that doping effect of iodine. Heterojuction is confirmed by rectifying current-voltage characteristics of a-C:I/n-Si junction. The decreasing of optical band gap from 0.54 to 0.25 eV after iodine doping was determined which contribute to induce graphitization in the films. Raman result indicates that sp2 and sp3 bonded carbon atoms were dominated in the both with and without iodine doped thin films.

Raman and Electrical Analysis of Iodine-Doped Amorphous Carbon Thin Films

Iodine doped amorphous carbon (a-C: I) thin films were prepared by using Thermal Chemical Vapor Deposition (CVD) with deposition temperature ranging from 5000C to 7000C. The physical and electrical properties of deposited a-C:I thin films were characterized by Raman spectroscope and Solar Simulator system. The presence of 2 peaks known as Raman D peaks and Raman G peaks ensure the amorphous structure of carbon (C). As deposition temperature increase, the ID/IG ratio shows difference value, which indicates the effects of the temperature towards the a-C: I structures. An ohmic graph was obtained for the IV measurement, and the conductivity varies from 10-4 to 101 Scm-1. The photoresponse was also determined for all samples. As a reference, an undoped a-C thin film was prepared to differentiate the characteristic between a-C and a-C: I.

Analysis on electrical and optical properties of nitrogen incorporated amorphous carbon prepared by aerosol-assisted CVD method

We have successfully deposit the a-C and nitrogen doped a-C (a-C:N) using the custom-made Aerosol-assisted CVD (AACVD). Natural precursor, camphor oil (C10H16O) was selected as the carbon source. The electrical and optical properties were characterized by BUKOH KEIKI CEP2000 solar simulator system and Perkin Elmer LAMBDA 750 UV-vis-NIR spectroscope respectively. Five samples were prepared for the a-C and a-C: N respectively, with the deposition temperatures ranging from 400°C to 600°C. An ohmic contact was acquired between the carbon/metal configurations from the current-voltage solar simulator system. Higher conductivity at a-C: N, ~x10-2 Scm-1 is due to the decrease in defects since the spin density gap decrease with the nitrogen addition. Pure a-C exhibit absorption coefficient, a of 10 cm-1, whereas for a-C:N, a is of 10 cm-1. The high σ value is at a-C:N is due to the presence of more graphitic component (sp2 carbon bonding) in the carbon films.

Nitrogen Incorporation of Nanostructured Amorphous Carbon Thin Films by Aerosol-Assisted Chemical Vapor Deposition

Nanostructured pure a-C and nitrogen doped a-C: N thin films with small particle size of, ~50 nm were obtained by Aerosol-assisted CVD method from the natural precursor camphor oil. Five samples were prepared for the a-C and a-C: N respectively, with the deposition temperatures ranging from 400℃ to 600℃. At high temperature, the AFM clarifies an even smoother image, due to the increase of the energetic carbon ion bombardment at the surface of the thin film. An ohmic contact was acquired from the current-voltage solar simulator characterization. The higher conductivity of a-C: N, of ~×10 -2 Scm -1 is due to the decrease in defects since the spin density gap decrease with the

Influence of Iodine Doping on the Properties of Amorphous Carbon Thin Films Deposited from Camphoric Carbon Precursor

odine incorporation to amorphous carbon (a-C) thin films offers many advantages and a full understanding of the properties of iodine doped amorphous carbon (a-C:I) thin films which is necessary for applications like optoelectronics devices and photovoltaic solar cells. Iodine doped amorphous carbon thin films have been doped by thermal chemical vapour deposition (CVD) technique at different amount of iodine. The effects of iodine amount on the properties of a-C:I thin films have been investigated using standard measurement techniques and discussed. FESEM studies have been performed on the doped films for the surface morphology studies. Raman studies have been carried out on the doped samples for the chemical bonding of carbon atoms. The sp2 and sp3 contents have found to be dependent on the amount of iodine. For evaluation of the electrical and optical properties of the doped films, the current-voltage (I-V) measurement and UV-Vis-NIR spectroscopy have been performed on the a-C:I thin films. It has been observed that the a-C:I thin films doped with 1g has higher electrical conductivity and lowest optical band gap.