Changdong Ma

Lattice modification in KTiOPO4 by hydrogen and helium sequentially implantation in submicrometer depth

We investigated lattice modification and its physical mechanism in H and He co-implanted, z-cut potassium titanyl phosphate (KTiOPO4). The samples were implanted with 110 keV H and 190 keV He, both to a fluence of 4 × 1016 cm−2, at room temperature. Rutherford backscattering/channeling, high-resolution x-ray diffraction, and transmission electron microscopy were used to examine the implantation-induced structural changes and strain. Experimental and simulated x-ray diffraction results show that the strain in the implanted KTiOPO4 crystal is caused by interstitial atoms. The strain and stress are anisotropic and depend on the crystals orientation. Transmission electron microscopy studies indicate that ion implantation produces many dislocations in the as-implanted samples. Annealing can induce ion aggregation to form nanobubbles, but plastic deformation and ion out-diffusion prevent the KTiOPO4 surface from blistering.

Micro-structure analysis of He+ ion implanted KTP by TEM

Micro-structure of high dose He-implanted x-cut KTP is investigated. Rutherford backscattering spectroscopy/channeling (RBS/Channeling) and transmission electron microscopy (TEM) are used to examine the structural and lattice damage properties in KTP after 200keV He+-implantation and following thermal annealing. Lattice crack, lattice disorder and He-bubble are observed in different implantation regions. The results show that strain induced by implantation is released through non-elastic lattice deformation in KTP. The implications of these observations for KTP thin film fabrication by smart-cut method are discussed.

Fabrication and analysis of single-crystal KTiOPO 4 films with thicknesses in the micrometer range

Single-crystal potassium titanyl phosphate (KTiOPO4, KTP) films with thicknesses less than 5 μm are obtained by using helium (He) implantation combined with ion-beam-enhanced etching. A heavily damaged layer created by a 4×10(16)  cm(-2) fluence of 2 MeV He implantation is removed by means of wet chemical etching in hydrofluoric acid (HF). Thus, free-standing films of KTP with thicknesses in the range of 3-5 μm are obtained. The etching rate can be adjusted over a wide range by choosing temperature and HF concentration, as well as annealing conditions. Sharp etching edges and the smooth surface of the film indicate that a high selective-etching rate is achieved in the damaged layer, and the remaining part of the crystal is undamaged. X-ray and Raman-scattering results prove that KTP films have good single-crystal properties.

Visualized strain profile in the process of crystal ion slicing of LiTaO3

LiTaO3 samples are implanted with 190KeV He and 110 KeV H with fluences in the range 2 × 1016–6 × 1016 cm−2 at room temperature. Lattice damage and strain caused by ion implantation and their change with annealing temperature are characterized by Rutherford backscattering spectrometry, high resolution x-ray diffraction and transmission electron microscopy. Strain distributions are illustrated by comparing simulated x-ray diffractive curves to the experimental results. In contrast to a broad strain distribution in H implanted samples, strain distribution is very concentrated in He-only or He-first co-implanted samples. Microfractures are caused in He-first samples due to severe lattice damage and large lattice strain. The strong coalescence effect of He ions in co-implanted LiTaO3 is analyzed and the mechanism of built-up high normal strain is proposed.

Suppression effect of silicon (Si) on Er3+ 1.54μm excitation in ZnO thin films

We have investigated the photoluminescence (PL) characteristics of ZnO:Er thin films on Si (100) single crystal and SiO2-on-silicon (SiO2) substrates, synthesized by radio frequency magnetron sputtering. Rutherford backscattering/channeling spectrometry (RBS), X-ray diffraction (XRD) and atomic force microscope (AFM) were used to analyze the properties of thin films. The diffusion depth profiles of Si were determined by second ion mass spectrometry (SIMS). Infrared spectra were obtained from the spectrometer and related instruments. Compared with the results at room temperature (RT), PL (1.54μm) intensity increased when samples were annealed at 250°C and decreased when at 550°C. A new peak at 1.15μm from silicon (Si) appeared in 550°C samples. The Si dopants in ZnO film, either through the diffusion of Si from the substrate or ambient, directly absorbed the energy of pumping light and resulted in the suppression of Er3+ 1.54μm excitation. Furthermore, the energy transmission efficiency between Si and Er3+...