Abdelrahman Zkria - JP - LASER ANNEALING OF DIAMOND MATERIALS

laser-assisted modifications of diamond materials

laser-matter interaction offers an important way to study material properties and to understand the intrinsic microstructure of materials.

Mechanism: When the material is irradiated with lasers, the laser energy will be firstly transformed into electronic excitation energy and then transferred to lattices of materials through collisions between electrons and lattices.

In material sciences, laser irradiation has been studied for various applications, including the Surface ﬁnishing method for steel molds by using a picosecond pulsed laser irradiation. Pulsed laser crystallization technique, enabling large area crystallization of a-Si to produce grains having well-defined size and orientation. Reduction of graphite oxide (GO) to graphene induced by picosecond pulsed laser irradiation.

ArF (argon fluoride) laser is a type of excimer laser that emits ultraviolet (UV) light with a wavelength of 193 nm, this laser irradiation can also induce changes in the material's surface morphology and structure. These changes can be useful in creating surface structures for various applications, such as anti-reflection coatings, microfluidic devices, and sensors.

In this project, we are studying the laser-induced structural modifications of different diamond-related materials, including Diamond-like carbon (DLC), Nanodiamond and Singlecrystalline Diamond

Pulsed Laser annealing of Diamond like carbon (DLC)

Non-hydrogenated amorphous carbon (or DLC) films were prepared by cathodic arc ion plating technique on cemented-tungsten carbide (WC-Co) (Co 5%) substrates. DLC/WC-Co annealed by applying a single pulse of ArF laser (λ = 193 nm; FWHM= 20 ns) at different energy densities.

Upon laser annealing, Raman spectra depicted higher sp3 fractions accompanied by a blue shift in the G-peak position, which indicates the changes of sp2 sites from rings to chains. At higher fluence, the film converts into reduced graphene oxide (rGO) film confirmed by its Raman-active vibrational modes: D, G, and 2D.

The results are presented in the research letter with Narayan's group, NCSU: [MRS Communication 9 (2019) 910–915]

Pulsed Laser annealing of Nanodiamond composite films

Hydrogenated Nanodiamond composite films were prepared by coaxial arc plasma deposition method on Si substrates, followed by ArF laser annealing.

The films revealed hydrogen effusions accompanied by the transformation of sp3 into sp2-hybridization carbon. However, the film irradiated at 0.8 J cm−2 exhibited higher sp3 fractions.

These results are presented in the research letter:

[Applied Physics Express 13, 105503 (2020)]

Laser-induced dopings and modifications on the surface of Diamond

In this research, we were able to create a conducive thin layer on the surface of a Single-crystal diamond (SCD ) by ArF laser irradiation. The SCDs were immersed in a dopant solution (Phosphoric acid /or Boric acid), followed by laser irradiation in a controllable process.

This alternative method of shallow-level doping has many advantages over other conventional methods, including:

+ low thermal-damage doping could be possible using this technique due to its local and very short heating mechanism.

+ Liquid dopant source offers a wide variety of dopants and provides a higher dopant density than gas sources.

[ACS Appl. Mater. Interfaces 2020, 12, 57619−57626 (2020)]

This method was used to form a novel ohmic contact for diamond devices. The low activation energy (<54 meV) of irradiated surfaces enabled space-charge-free build-up effects between the diamond and the external connection. The laser treatment of diamond films displayed promising results for the fabrication of diamond detectors with minimum power consumption, fastest process rate, and highest visible-light detection that could maintain smooth and stable charge transport. [Materials Science in Semiconductor Processing, 139, 106370 (2022)]

Finally, we succeeded on the fabrication of p-n+ diamond homojunction through the laser irradiation in liquid-ambient. A shallow phosphorus-doped layer with a high electric conductivity is processed on top of a p-type diamond substrate to form the p-n+ homojunction. [Materials Research Letters 10, 666-674 (2022)]

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