Characterisation of Diamond-Like Carbon (DLC) laser targets by Raman spectroscopy

5th Target Fabrication Workshop

Haddock, D.^1 ; Parker, T.^1 ; Spindloe, C.^1 ; Tolley, M.^1

Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Oxon-Chilton

OX11 0QX, United Kingdom^1

关键词: Central laser facilities;    Diamond like carbon;    Gas flow mixtures;    Laser prepulses;    Low-Z materials;    Plasma enhanced chemical vapour deposition;    Target chambers;    Target materials;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/713/1/012007/pdf
DOI  :  10.1088/1742-6596/713/1/012007

来源: IOP

【 摘 要 】

The search for target materials suitable for High Power Laser Experiments at ultralow thicknesses (below ten nanometres) is ongoing. Diamond-Like Carbon is investigated as an answer for a low-Z material that can survive target chamber pump-down and laser prepulse. DLC was produced using Plasma-Enhanced Chemical Vapour Deposition, using with varying gas flow mixtures of argon and methane. The methane plasma deposits amorphous carbon onto the substrate and the argon plasma re-sputters the weakly bonded carbon leaving a high proportion of diamond-like bonding. Bonding natures were probed using Raman spectroscopy; analysis of the resulting spectrum showed that flow rates of 40sccm/60sccm methane to argon produced DLC films with a diamond-like (sp3) content of ∼20%. Increasing the methane gas flow decreased this value to less than 5%. DLC foils were processed into laser targets by method of float off; using a sodium chloride release layer and lowering into water, this was then lifted onto an array of apertures allowing for laser irradiation of the material with no backing. DLC with 20% sp3content showed superior yield when compared to other materials such as metals and some plastics of the same thickness, with ∼70% of the target positions surviving the float off procedure at