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Optical and Electrical Properties of Diamond-like-Carbon Coatings Prepared by Electron Cyclotron Resonance Ion Beam Deposition Process
Authors:
Callum Wiseman,
Marwa Ben Yaala,
Chalisa Gier,
Laurent Marot,
Christopher McCormick,
Caspar Clark,
Sheila Rowan,
Stuart Reid
Abstract:
Diamond-like carbon thin films have emerged as durable, chemically stable optical coatings for many optical and optoelectronics applications due to their hardness, chemical inertness, and optical transparency. This paper presents a novel high-energy electron cyclotron resonance ion beam sputter deposition technique to fabricate pure diamond-like carbon coatings at room temperature. The chemical co…
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Diamond-like carbon thin films have emerged as durable, chemically stable optical coatings for many optical and optoelectronics applications due to their hardness, chemical inertness, and optical transparency. This paper presents a novel high-energy electron cyclotron resonance ion beam sputter deposition technique to fabricate pure diamond-like carbon coatings at room temperature. The chemical composition of the deposited coatings including ratios of sp2/sp3 bonding in the thin films were determined by X-ray photoelectron spectroscopy. Results indicate that the sp3 percentage ranges from 45% - 85%. The transmission and reflectance spectra of the coatings were measured from UV to IR (λ= 185 to 2500 nm) by utilizing a spectrophotometer. The measured spectra were analysed by the Tauc method to determine the optical band gap and Urbach energy and an optical fitting software, which utilizes the model modified by OJL, to extract the refractive index and extinction coefficient. By varying the ion energy, the optical properties were found to be n = 2.30 - 2.51, band gap energy = 0.4 - 0.68 eV, and the Urbach energy = 0.33 - 0.49 eV. This study provides a flexible method for tuning the structural, optical, and electronic properties of diamond-like carbon coatings by controlling the ion energy during deposition.
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Submitted 11 June, 2024;
originally announced June 2024.
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Ion Energy Tuning for Enhanced sp3 Carbon Fraction in Electron Cyclotron Resonance Ion Beam Deposited Diamond-Like Carbon Coatings: a Computational and Experimental Approach
Authors:
Callum Wiseman,
Marwa Ben Yaala Chalisa Gier,
Laurent Marot,
Christopher McCormick,
Sheila Rowan,
Stuart Reid
Abstract:
A novel high-energy electron cyclotron resonance (ECR) ion beam deposition (IBD) technique was used to fabricate DLC films at different ion beam energies. The ratios of sp2/sp3 bonding in the DLC coatings were determined by Raman spectroscopy and XPS, with the confirmation of being hydrogen-free due to the lack of photoluminescence (PL) background in the Raman spectra. The results indicate that th…
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A novel high-energy electron cyclotron resonance (ECR) ion beam deposition (IBD) technique was used to fabricate DLC films at different ion beam energies. The ratios of sp2/sp3 bonding in the DLC coatings were determined by Raman spectroscopy and XPS, with the confirmation of being hydrogen-free due to the lack of photoluminescence (PL) background in the Raman spectra. The results indicate that the sp3 percentage ranges from 45% - 85% for the ECR-IBD fabricated DLC films in this study. Monte-Carlo based SRIM simulation was used to extract the energy and angular distribution of the sputtered particles from the carbon target and correlate it to the highest sp3 fraction in the manufactured ECR-IBD DLCs. This study demonstrates a method of depositing DLC thin films under ambient conditions (room temperature with no post-annealing or additional bias voltage applied) which produces high-sp3 coatings (higher than those traditionally reported for other sputtering methods) suitable for applications where high quality DLC coatings are required.
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Submitted 11 June, 2024;
originally announced June 2024.
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Anisotropic Etching of Graphite and Graphene in a Remote Hydrogen Plasma
Authors:
Dorothee Hug,
Simon Zihlmann,
Mirko K. Rehmann,
Yemliha B. Kalyoncu,
Timothy N. Camenzind,
Laurent Marot,
Kenji Watanabe,
Takashi Taniguchi,
Dominik M. Zumbühl
Abstract:
We investigate the etching of a pure hydrogen plasma on graphite samples and graphene flakes on SiO$_2$ and hexagonal Boron-Nitride (hBN) substrates. The pressure and distance dependence of the graphite exposure experiments reveals the existence of two distinct plasma regimes: the direct and the remote plasma regime. Graphite surfaces exposed directly to the hydrogen plasma exhibit numerous etch p…
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We investigate the etching of a pure hydrogen plasma on graphite samples and graphene flakes on SiO$_2$ and hexagonal Boron-Nitride (hBN) substrates. The pressure and distance dependence of the graphite exposure experiments reveals the existence of two distinct plasma regimes: the direct and the remote plasma regime. Graphite surfaces exposed directly to the hydrogen plasma exhibit numerous etch pits of various size and depth, indicating continuous defect creation throughout the etching process. In contrast, anisotropic etching forming regular and symmetric hexagons starting only from preexisting defects and edges is seen in the remote plasma regime, where the sample is located downstream, outside of the glowing plasma. This regime is possible in a narrow window of parameters where essentially all ions have already recombined, yet a flux of H-radicals performing anisotropic etching is still present. At the required process pressures, the radicals can recombine only on surfaces, not in the gas itself. Thus, the tube material needs to exhibit a sufficiently low H radical recombination coefficient, such a found for quartz or pyrex. In the remote regime, we investigate the etching of single layer and bilayer graphene on SiO$_2$ and hBN substrates. We find isotropic etching for single layer graphene on SiO$_2$, whereas we observe highly anisotropic etching for graphene on a hBN substrate. For bilayer graphene, anisotropic etching is observed on both substrates. Finally, we demonstrate the use of artificial defects to create well defined graphene nanostructures with clean crystallographic edges.
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Submitted 14 March, 2017;
originally announced March 2017.
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Pico- and nanosecond laser ablation of mixed tungsten / aluminium films
Authors:
M. Wisse,
L. Marot,
R. Steiner,
D. Mathys,
A. Stumpp,
M. Joanny,
J. M. Travere,
E. Meyer
Abstract:
In order to extend the investigation of laser-assisted cleaning of ITER-relevant first mirror materials to the picosecond regime, a commercial laser system delivering 10 picosecond pulses at 355 nm at a frequency of up to 1 MHz has been used to investigate the ablation of mixed aluminium (oxide) / tungsten (oxide) layers deposited on poly- and nanocrystalline molybdenum as well as nanocrystalline…
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In order to extend the investigation of laser-assisted cleaning of ITER-relevant first mirror materials to the picosecond regime, a commercial laser system delivering 10 picosecond pulses at 355 nm at a frequency of up to 1 MHz has been used to investigate the ablation of mixed aluminium (oxide) / tungsten (oxide) layers deposited on poly- and nanocrystalline molybdenum as well as nanocrystalline rhodium mirrors. Characterization before and after cleaning using scanning electron microscopy (SEM) and spectrophotometry shows heavy dust formation, resulting in a degradation of the reflectivity. Cleaning using a 5 nanosecond pulses at 350 and 532 nm, on the other hand, proved very promising. The structure of the film remnants suggests that in this case buckling was the underlying removal mechanism rather than ablation. Repeated coating and cleaning using nanosecond pulses is demonstrated.
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Submitted 17 April, 2014;
originally announced April 2014.
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Quantum Hall effect in graphene with superconducting electrodes
Authors:
Peter Rickhaus,
Markus Weiss,
Laurent Marot,
Christian Schönenberger
Abstract:
We have realized an integer quantum Hall system with superconducting contacts by connecting graphene to niobium electrodes. Below their upper critical field of 4 tesla, an integer quantum Hall effect coexists with superconductivity in the leads, but with a plateau conductance that is larger than in the normal state. We ascribe this enhanced quantum Hall plateau conductance to Andreev processes at…
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We have realized an integer quantum Hall system with superconducting contacts by connecting graphene to niobium electrodes. Below their upper critical field of 4 tesla, an integer quantum Hall effect coexists with superconductivity in the leads, but with a plateau conductance that is larger than in the normal state. We ascribe this enhanced quantum Hall plateau conductance to Andreev processes at the graphene-superconductor interface leading to the formation of so-called Andreev edge-states. The enhancement depends strongly on the filling-factor, and is less pronounced on the first plateau, due to the special nature of the zero energy Landau level in monolayer graphene.
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Submitted 14 March, 2013;
originally announced March 2013.
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Erosion yields of carbon under various plasma conditions in Pilot-PSI
Authors:
K. Bystrov,
J. Westerhout,
M. Matveeva,
A. Litnovsky,
L. Marot,
E. Zoethout,
G. De Temmerman
Abstract:
Fine-grain graphite targets have been exposed to ITER divertor relevant plasmas in Pilot-PSI to address material migration issues in fusion devices. Optical emission spectroscopy and mass loss measurements have been employed to quantify gross chemical erosion and net erosion yields, respectively. Effects of the ion impact energy and target geometry on carbon erosion yields have been studied. It is…
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Fine-grain graphite targets have been exposed to ITER divertor relevant plasmas in Pilot-PSI to address material migration issues in fusion devices. Optical emission spectroscopy and mass loss measurements have been employed to quantify gross chemical erosion and net erosion yields, respectively. Effects of the ion impact energy and target geometry on carbon erosion yields have been studied. It is concluded that temporal evolution of gross chemical erosion is strongly connected with changes in morphology of plasma exposed surfaces. The net carbon erosion yield is increased when the targets are partly covered by insulating boron-nitride rings.
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Submitted 12 October, 2012;
originally announced October 2012.