Figure 2 Current–voltage characteristics of Ge sample and plot of d (V) / d
(ln J ) and H (J). I-V characteristics (curve 1) before and after irradiation (curve 2) by Nd:YAG laser at intensity I = 1.15 https://www.selleckchem.com/products/sn-38.html MW/cm2 and wavelength λ = 266 nm. (1, A) Plot of d(V) / d(ln J) and H(J) depending on current density J according to [21]. Figure 3 AFM image of irradiated semiconductor surfaces. 3D AFM image of Ge surface irradiated by Nd:YAG laser at intensity 7.0 MW/cm2. Figure 4 Dynamics of nanocones formation by laser radiation in intrinsic semiconductors. (1–8) Schematic images of dynamics of nanocones formation by laser radiation in intrinsic semiconductors. Microcones It is known that microcones of Si can absorb more than 95% of incident light [22] because in array of microcones, light is repeatedly reflected between the microcones and is absorbed almost completely, and a single Si crystal check details reflects visible light by 30% [23]. The microstructured surface is completely black to the naked eye (see Figure 5). Therefore, Si with microcones is known as black Si [24]. Black Si is an excellent material for solar cells [22]. Solar cells with microcones
are proved to be more efficient, generating more current than the conventional one. Also, black Si can be used to make infrared detectors, which is a new application for Si [24]. Figure 5 A photo of real sample of Ni/Si structure after irradiation by Nd:YAG laser. A photo of real sample of Ni/Si structure after irradiation by Nd:YAG laser. The black areas contain microcones formed by laser radiation. The surface microstructuring of ordinary Si by pulsed femtosecond laser-induced plasma
[25, 26] or chemical vapor deposition with catalytic metal on Si [27] is used for black Si formation. We proposed a new laser method, which is simpler and cheaper comparison with above-mentioned methods [11]. In our experiments, after Ni/Si structure irradiation by Nd:YAG laser, various degrees of damage are observed on the surface of the Ni/Si, such as the appearance of cracks and formation of small Cepharanthine (several microns) Ni islands, as shown in Figure 6a. The Nd:YAG laser intensity threshold, at which the self-organization of cone-like microstructures with the size of 3.15 MW/cm2, was observed on the surface of Ni/Si layer system. The further increase of the laser intensity and number of pulses lead to the formation of cone-like microstructures and maximal height of the cone of about 100 μm. The control of the microcone shape and height was achieved by changing the intensity of laser radiation and a number of pulses (Figure 6b,c) [11]. Figure 6 SEM images of Ni/Si surface irradiated by Nd:YAG laser. SEM images of Ni/Si surface irradiated by Nd:YAG laser at intensity 4.5 MW/cm2: 3 laser pulses per point (a), 10 laser pulses per point (b), and 22 laser pulses per point (c).