Next, the nanobelts were transformed on another silicon chip, and Au markers NVP-BSK805 had been produced on the silicon chip in advance through photolithography. The prepared samples were mounted into the vacuum chamber of the ion implanter and implanted by N+ ions with
30 keV. The choice implantation fluences include 5 × 1015, 1 × 1016, and 5 × 1016 ions/cm2. The photoluminescence spectra of every marked CdS nanobelts were detected by the micro-Raman system (LabRAM HR800, HORIBA Ltd., Minami-Ku, Kyoto, Japan) both before and after ion implantation. Surface morphology images of CdS nanobelts were acquired through SEM (FEI Sirion FEG, FEI Company, Hillsboro, OR, USA). Figure 13a,b shows schematic diagrams of the transfer process and implantation process, respectively. Figure 13c,d,e displays the SEM and optical image of the CdS nanobelts. Figure 13 Schematic diagram and optical and SEM images of processes. The schematic diagram of (a) the transform process and (b) implantation process. (c, d) The optical and (e)
SEM image of the nanobelts grown by thermal evaporation process. Figure 14 shows the PL emission spectrum of single CdS nanobelts at room temperature. All the curves in Figure 14a signify the PL emission spectrum of the same nanobelt; Figure 14b,c represents two other nanobelts. In the case of the dose of 5 × 1015 ions/cm2, the PL emission spectrum of the unimplanted nanobelt has three emission peaks at about 505, 617, and 770 nm. The peak at
505 nm originates from the near-band-edge emission of CdS, and the broad emission band at 617 nm is associated with the low density of LY333531 sulfur vacancies in the CdS nanobelt [65]. The peak at www.selleckchem.com/products/SB-202190.html 770 nm is related to the transitions between the surface states and the valence band of CdS [66, 67]. After ion implantation, the near-band-edge emission peak was red-shifted, and the defect emission Morin Hydrate peak was quenched. Later, all the samples were annealed in an argon atmosphere at 350°C for 40 min. The crystalline quality of the CdS nanobelts recovered obviously after annealing in argon atmosphere. In the red emission region, the annealed nanobelts have an emission peak at 750 nm. This may be attributed to the surface defect similar to that of unimplanted nanobelts and/or the high density of sulfur vacancies caused by ion implantation [65, 68]. Unimplanted nanobelts have a defect emission peak at 617 nm caused by a small number of sulfur vacancies generated during growth process. After ion implantation and the annealing process, the concentration of sulfur vacancies increased observably; although the annealing process could recover the crystal lattice and reduce sulfur vacancies, a mass of sulfur vacancies still remained in the lattice after annealing. The emission peak at 526 nm may be attribute to the N+ ions implanted into the crystal lattice and substituted S as a shallow acceptor; this process resulted in the red shift of the band-edge emission peak.