Laser plasma source of amorphic diamond

Collins, C. B.; Davanloo, F.; Juengerman, E. M.; Osborn, William Robert; Jander, D. R.

doi:10.1063/1.101013

Cited by 91 publications

(18 citation statements)

References 10 publications

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“…In the literature, other names have been used to label carbon films which are structurally virtually identical to a-tC, including ta-C 1 and amorphic diamond. 8 In the remainder of the text, we will refer to these films only as a-tC. For stress relaxation studies, the a-tC films were deposited on 2" Si (100) wafers treated prior to deposition by brief immersion in dilute HF.…”

Section: Methodsmentioning

confidence: 99%

Stress relaxation and thermal evolution of film properties in amorphous carbon

Sullivan

Friedmann

Baca

1997

Journal of Elec Materi

152

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A model for the stress relaxation of amorphous carbon films containing high concentrations of fourfold coordinated carbon is presented. The onset of stress relaxation in these materials occurs following thermal annealing at temperatures as low as 100~ and near full stress relaxation occurs after annealing at 600~ The stress relaxation is modeled by a series of first order chemical reactions which lead to a conversion of some fourfold coordinated carbon atoms into threefold coordinated carbon atoms. The distribution of activation energies for this process is derived from the experimental measurements of stress relaxation and is found to range from 1 eV to over 3 eV. Permanent increases in the electrical conductivity of the carbon films are also found following thermal annealing. The electrical conductivity is found to be exponentially proportional to the number of additional threefold atoms which are created upon annealing, with the increase in threefold atom concentration being deduced from the stress relaxation model. This indicates that the increase in electrical conductivity and the stress relaxation originate from the same fourfold to threefold conversion process and that electrical transport through these films is dominated by a hopping conduction process.

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Section: Methodsmentioning

confidence: 99%

Stress relaxation and thermal evolution of film properties in amorphous carbon

Sullivan

Friedmann

Baca

1997

Journal of Elec Materi

152

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“…DLC films are free of hydrogen, extremely hard, and consist of sp 3 C-C bond fractions higher than 70%. [4][5][6] It is known that the degree of diamondlike character of the films is closely related to the deposition parameters such as substrate temperature, background pressure, as well as laser wavelength and intensity. Considerable studies have been made to improve the physical properties of DLC films, either by varying the laser power density 5 or using an auxiliary energy source.…”

Section: Introductionmentioning

confidence: 99%

Effect of laser intensity on the properties of carbon plasmas and deposited films

Ong

Chang

1997

Phys. Rev. B

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The effect of laser intensity on the deposition of diamondlike carbon ͑DLC͒ films has been studied using an ArF ͑193 nm͒ pulsed excimer laser. Our results are found to be distinct from other studies using Nd-YAG infrared or excimer 248-nm lasers. Two issues concerning the growth mechanism of the films are discussed: ͑1͒ the dynamics of the laser-induced plasma and ͑2͒ the dependence of the nature of the deposited films on laser intensity. To address the first issue, time-integrated optical emission spectroscopy has been carried out to investigate the carbon plasma induced by the ArF ͑193 nm͒ laser. Instead of molecular carbon bands ͑C 2 ͒, monoatomic neutral ͑C I ͒ and ionic ͑C II ͒ emission lines are found to dominate the spectra. The emissions of ͑C I ͒ and ͑C II ͒ have been studied as a function of laser intensity. For low laser intensity, the laser irradiation removes the target surface material primarily through thermal evaporation. When the laser intensity is above a threshold of ͑3.7-4͒ϫ10 8 W/cm 2 , the evaporated species are also ionized. The observed phenomenon can be attributed to higher multiphoton ionization and inverse bremsstrahlung rate as the laser intensity is increased. For the second issue, films deposited at various intensities have been characterized by ellipsometry. Results show that films deposited at low intensity are found to have excellent optical transparency ͑E g ϭ2.3 eV͒, which implies a considerable amount of sp 3 bonds. However, films deposited at higher intensities are found to be more graphitic. The damage threshold has also been located at 3.7ϫ10 8 W/cm 2 . A qualitative structural analysis based on the effective-medium approximation has been performed on the deposited films to investigate the influence of laser intensity on their microstructures. ͓S0163-1829͑97͒01407-0͔

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“…For a-DLC films without hydrogen, the band gap usually decreases monotonically with increasing temperature due to the conversion of diamond-like sp 3 bondings into graphitic sp 2 bondings. 11 However, the a-DLC:H films which we obtained show a maximum band gap near a temperature window of 100-200°C. To correlate the variation of the band gap with the amount of sp 3 in the film, we have plotted the ratio of sp 3 /sp 2 as a function of deposition temperature in Fig.…”

Section: B Optical Properties and Band Gapmentioning

confidence: 69%

“…11 The source materials are either carbon-containing gases or a pure solid graphite target and occasionally poly-mer targets. 12 Due to low-energy bombardment, the films deposited by conventional sputtering techniques usually yield large amounts of sp 2 or graphitic bondings, an unwanted structure for a-DLC:H applications.…”

Section: Introductionmentioning

confidence: 99%

Pulsed laser deposition of hydrogenated amorphous diamond-like carbon films from a polymer target

Yang

Xiao

1996

Journal of Applied Physics

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Growth of caxis oriented gallium nitride thin films on an amorphous substrate by the liquidtarget pulsed laser deposition technique Diamondlike carbon films grown by very high frequency (100 MHz) plasma enhanced chemical vapor deposition technique Appl.Structural and optical properties of laser deposited ferroelectric (Sr0.2Ba0.8)TiO3 thin films Hydrogenated amorphous diamond-like carbon ͑a-DLC:H͒ films have been prepared by pulsed laser ablation of a polymer target in the presence of hydrogen ͑H 2 ͒ gas. The growth rate of these films was found to be highly dependent on the deposition temperature and the amount of H 2 gas used during the deposition process. The optical band gap of these a-DLC:H films changed in a wide range ͑0.25-2.5 eV͒ with substrate temperature and H 2 pressure, and was found to be highly correlated to the ratio of sp 3 /sp 2 in the film. The gap reached a maximum in a temperature range between 100 and 200°C and had small values at either lower or higher temperatures. With increasing H 2 pressure, the band gap increased monotonically and saturated around 0.5 mbar. It was found that the refractive index and the imaginary part of dielectric constant of these a-DLC:H films monotonically increased with decreases in the wavelength of the probing beam. It was also found that these laser derived a-DLC:H films could be made either completely insulating ͓ϳ10 Ϫ11 ͑⍀ cm͒ Ϫ1 ͔ or conducting ͓ϳ1 ͑⍀ cm͒ Ϫ1 ͔ by simply varying the deposition temperature and H 2 pressure. Very little photoconduction has been observed in these a-DLC:H films.

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Laser plasma source of amorphic diamond

Cited by 91 publications

References 10 publications

Stress relaxation and thermal evolution of film properties in amorphous carbon

Stress relaxation and thermal evolution of film properties in amorphous carbon

Effect of laser intensity on the properties of carbon plasmas and deposited films

Pulsed laser deposition of hydrogenated amorphous diamond-like carbon films from a polymer target

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