# Fabrication of Smart Materials Using Laser Processing: Analysis and Prospects
## 3 Harnessing Photothermal Reactions and Functional Additive Introduction
This approach allows for the creation of materials with unique functional characteristics, making them customizable for various applications. Notably, in [116], the laser doping method was employed, with the application of an ultraviolet nanosecond laser, to co-dope with fluorine and induce an N-type transition in phosphorus-doped germanium. Similarly, in [117], laser doping was used for nitrogen doping in 4H-silicon carbide. A KrF excimer laser with a wavelength of 248 nm was utilized in the experimental study. The pulse duration was 82 ns, while the repetition frequency was set to 100 Hz. Employing a slit, the laser beam was narrowed near the center, creating an area of 300 \(\times\) 300 \(\upmu\)m on the sample surface. During the experiment, the laser irradiation frequency ranged from 1 to 200 shots per location by adjusting the sample scanning speed. The laser irradiation fluence was set within the range of 2.2 to 3.4 J cm\({}^{-2}\). In [118], this method was applied for heavy doping of thin silicon-on-insulator layers in conjunction with laser thermal annealing. These examples underscore the versatility of laser doping as a mean for modifying electronic properties in different materials for specific applications. It is worth noting that annealing plays a pivotal role in the semiconductor industry, serving as a critical process for optimizing semiconductor material properties. Annealing involves controlled heating and cooling to enhance the crystalline structure, minimize defects, and manage electrical characteristics. To meet the growing demand for low total heat input methods, especially driven by innovations like 3D integrated circuits, pulsed laser annealing has emerged as a promising technique. Pulsed laser annealing offers high dopant activation levels and minimal surface roughness, making it well-suited for various semiconductor applications [119]. Numerous studies delve into the applications of laser annealing. In [120], the paper discussed the preparation and characterization of ZnO nanofilms (ZNFs) on silicon substrates using a sol-gel-assisted spin-coating process. These ZNFs were modified by Nd:YAG pulsed laser annealing at specific wavelengths, resulting in improved structure and electrical properties. The samples were exposed to Nd:YAG laser beams at varying wavelengths, specifically 1064 nm, 532 nm, and 355 nm. Each wavelength received 5 pulses, with an energy fluence of approximately 650 mJ/cm\({}^{2}\), a frequency of 1 Hz, laser energy set at 500 mJ, and a window area of about 0.8 cm\({}^{2}\). In [121], a comprehensive analysis of the green laser annealing method for phosphorus-doped silicon was presented. Additionally, the study in [122] highlighted the successful solid-phase recrystallization of partially amorphized silicon-on-insulator structures using pulsed ultraviolet nanosecond laser annealing. This approach achieved high dopant activation rates with a low overall heat input, positioning it as a promising technique for 3D sequential integration. In Figure 7, TEM images showcase a cross-section of a 22 nm-thick silicon-on-insulator structure with phosphorus implantation, revealing the impact of sub-melt multi-pulse ultraviolet nanosecond laser annealing (UV-NLA). The samples were processed with UV-NLA using a device equipped with a XeCl excimer laser with a wavelength of 308 nm. The laser had a pulse duration of 160 ns and operated at a frequency of 4 Hz. Spatial homogenization of the laser beam was performed to achieve consistent results, ensuring a non-uniformity level below 3%, and generating a top-hat beam, measuring 15 \(\times\) 15 mm\({}^{2}\). The observations highlight that 30 laser pulses at 0.58 J/cm\({}^{2}\) can induce partial recrystallization in the amorphous Si layer, while 100 pulses at the same energy density result in complete recrystallization. This emphasizes the efficacy of UV-NLA in a sub-melt multi-pulse mode, achieving a progressive solid-phase recrystallization of the amorphous layer from the crystalline seed.