PROJECT ABSTRACT
The presented project is directed to a detailed study and reveal of the process of laser-induced nitride ceramics decomposition and analysis of the obtained material properties. The realization of this effect may lead to a high spatial resolution modification and controlled formation of complex metal/dielectric or semiconductor/dielectric heterostructure materials. The ability of fabrication of such materials with spatial characteristics in micro- and nanometer range brings this method in the field of manufacturing materials with wide range of applications – from metamaterials to UV plasmonics. The characterization of the process of laser-induced decomposition of nitride and nitride ceramics from this point of view is a new idea.
The main goal of the project is the detailed description of the process of laser-induced decomposition of AlN and Si3N4 and characterization of obtained material. This includes reveal of the physical background of the involved processes as laser energy absorption, energy dissipation and heating of the material, corresponding reactions leading to change of the material and its properties. Other important direction is characterization of the properties of the formed material and structures as well as definition of key parameters that strongly can modify these properties.
The project goals implementation is based on experimental and theoretical studies. These include laser processing with nano- and picosecond pulses and a wide variation of the processing parameters that will allow definition of crucial ones and their values for fabrication of structures with desired properties. The theoretical study is based on development and application of numerical models that will describe the processes of laser-induced heating, thermal decomposition and optical properties of the fabricated structures.
The project duration is 36 month, as the work program consists of four Work packages. The budget for equipment considers purchase of modules for generation of second, third and the fourth harmonic of a picosecond Nd:YAG laser. They will contribute to execution of complex study of the process of laser-induced decomposition of ceramics at different conditions from one side, and in addition, will open a way for processing with a high and controllable precision, due to the strong influence of the material absorption on the laser wavelength. Purchase of a computer system that will be used for the theoretical studies based on numerical model development and the use of the available one is also considered.
Due to the complexity of processes involved, the project implementation will contribute to obtaining of new knowledge in different areas: interaction of laser radiation with composite materials, propagation of laser pulses in ceramic materials, mechanisms of light absorption and the induced materials modification, the phase changes in complex materials, fabrication of composite and heterostructured materials and their characterization. This study will also reveal the basic relations between these processes and their dependences on the processing conditions and the properties of the initial materials. Furthermore, a new knowledge in the field of picosecond laser pulses-ceramics interaction, as well as a comparative study with the basic processes for nanosecond processing will be obtained. The obtained results will give a detailed physical background of a new, original technology for fabrication of complex multifunctional materials with desired characteristics and novel applications as metamaterials, UV plasmonic sensors and Si photonics. Demonstrations of such properties are one of the main goals of the presented project.
RESEARCH TEAM
- Prof. DSc Nikolay Nedyalkov (coordinator)
Assoc. Prof. Anna Dikovska
Assoc. Prof. Mihaela Koleva
Assoc. Prof. Albena Daskalova
Assoc. Prof. Nadya Stankova
Assist. Prof. Rumen Nikov
Assist. Prof. Rosen Nikov
Assist. Prof. Tina Dilova
Physicist Liliya Angelova
Georgii Stanev
RECENT RESULTS
On the basis of the conducted experiments and analyzes of the main dependences in the laser processing of nitride ceramics - AlN and Si3N4 and of material formed on the surface after laser processing at a wide range of parameters, it was established that: The ablation of nitride ceramics - AlN and Si3N4 with nanosecond pulses is related to efficient decomposition of the material. The process can be written in terms of the reactions:
AlN → Al(liquid)+1/2N2(gas),
Si3N4 → 3Si(liquid)+2N2(gas).
Decomposition of ceramics is a thermal process, which is also effectively realized in the case of radiation with photon energy greater than the width of the forbidden zone. This process determines the formation of molten material on the surface of the ceramic. In the case of AlN ceramics, nanosecond processing at energy densities above thresholds results in the formation of an electrically conductive material composed primarily of Al. Within the framework of the research, parameters and areas of their values were defined, where the resistance of the obtained materials is minimal. Also, values are defined at which it can be changed within an order. Structures with different geometries were also considered, and conditions for obtaining minimum resistance and controlling its value were defined. It was established that the experimental conditions influence the morphology of the treated areas, and the main parameters and their values for obtaining structures with desired characteristics were determined. A characteristic morphology expressed in the obtaining of a periodic structure is described, and its characteristics and their dependence on the experimental conditions are clearly defined.
The nanosecond ablation of the Si3N4 ceramic leads to the formation of a silicon layer, which, depending on the experimental conditions, can be completely or partially oxidized. The main characteristics of the ablation process have been determined, and the parameters that affect them have been defined. Values of laser parameters were obtained at which structures with desired morphology and composition can be obtained. Research has shown that nanoscale Si objects can be produced in the interaction region. A theoretical model has been developed enabling the description of the temperature evolution and the implementation of various processes during the interaction of laser radiation with ceramics. Comparison of some parameters from the simulations with those obtained experimentally, such as ablation threshold, ablated depth, show good agreement. On the basis of a wide range of analytical techniques, a detailed analysis of the morphology, structure and composition of the material in the irradiation zone of AlN and Si3N4 nitride ceramics has been carried out. Initial experiments were conducted on laser ablation of nitride ceramics with picosecond pulses. The obtained results and knowledge enable the realization of applications in UV plasmonics and design of metamaterials for the THz region and photonics.
PUBLICATIONS
N.N. Nedyalkov, A. Dikovska, R. Nikov, G. Atanasov, S. Hayashi, M. Terakawa,
Laser-induced periodic structure formation in AlN ceramic,
Optics and Laser Technology 144 (2021) 107402, Q1, IF - 4.939 , SJR-0.85,
https://www.sciencedirect.com/science/article/pii/S0030399221004904?via%3Dihub N. Nedyalkov, A. Dikovska, L. Aleksandrov, M. Terakawa,
Nanosecond laser ablation of AlN ceramic,
Applied Physics A, 127 (2021) 951, Q2, IF - 2.983 , SJR – 0.44
https://link.springer.com/article/10.1007/s00339-021-05106-3 N.Nedyalkov, A.Dikovska, R.Nikov, Ro.Nikov, T.Dliova, G.Atanasova, L.Aleksandrov, D.Karashanova, V.Strijkova, M.Terakawa,
Nanosecond laser-induced oriented periodic structures on AlN ceramic,
Applied Surface Science, 585 (2022) 152712, Q1, IF – 7.392, SJR – 1.15
https://www.sciencedirect.com/science/article/pii/S0169433222002938?via%3Dihub N. Nedyalkov, A. Dikovska, K. Grochowska, R. Jendrajewski, L. Aleksandrov, T. Dilova, G. Atanasova,
Ablation and surface structuring of Si3N4 ceramics by nanosecond laser pulses,
accepted, Applied Physics A, Q2, IF - 2.983 , SJR – 0.44 N Nedyalkov, T Dilova, A Dikovska, Ru Nikov, Ro Nikov, M Koleva, N Stankova, Al Daskalova and L Angelova,
Laser processing of nitride ceramics,
2022 J. Phys.: Conf. Ser. 2240 012044, SJR – 0.21
https://iopscience.iop.org/article/10.1088/1742-6596/2240/1/012044 Ro Nikov, N Nedyalkov, T Nikova and L Aleksandrov,
Nanosecond laser ablation of nitride ceramics in liquid,
2022 J. Phys.: Conf. Ser. 2240 012048, SJR – 0.21
https://iopscience.iop.org/article/10.1088/1742-6596/2240/1/012048
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