Date of Graduation
A series of paramagnetic defects have been characterized in KH2 PO4 (KDP) and KTiOPO4 (KTP) using optical absorption, electron paramagnetic resonance (EPR), and electron-nuclear double resonance (ENDOR) techniques. In KDP, one hole-like center and five electronlike centers were investigated. Spin-Hamiltonian parameters were obtained for the holelike center and two electronlike centers. The hole center consists of a hole trapped on an oxygen ion adjacent to a silicon impurity substituting for a phosphorus ion. The electron centers are oxygen vacancies with one trapped electron, i.e., they are (PO3)2âˆ’ molecular units. Both the hole center and the electron centers can be formed at room temperature (or at 77 K) with x-rays or the fourth harmonic output (266 nm) of a Nd:YAG laser. Their EPR spectra are best observed at room temperature. These defects are stable for several weeks at room temperature. Also, in KDP, an Fe3+ paramagnetic defect characterized in an earlier work was revisited and a complete set of spin-Hamiltonian parameters, including fourth order, were determined. In KTP crystals, three platinum centers and two silver centers were identified. The platinum centers were produced by exposure to 355 nm laser light or by irradiation with x-rays, while the silver centers were produced with x-rays only. Spin-Hamiltonian parameters were determined for the three platinum centers. One of these defects is assigned to a Pt3+ ion (3d7 ) substituting for a Ti4+; it is formed when a Pt 4+ ion traps an electron. The other two platinum centers are suggested to be hole traps, and are formed when a hole is trapped at a Pt0 atom substituting for a K+ ion, which results in a Pt + ion (3d9). A silver center was characterized in KTP using ENDOR. Silver was diffused into the crystal during a post-growth anneal. It is suggested that Ag+ ions occupy K+ sites and upon irradiation with x-rays trap a hole, thus becoming Ag2+ ions. The various Pt and Ag centers characterized in the present investigation are stable at room temperature, and they may serve as charge compensators for other absorbing centers when KTP crystals are used in high-power laser applications.
Garces, Nelson Yovanny, "Analysis of paramagnetic point defects in potassium dihydrogen phosphate and potassium titanyl phosphate crystals." (2000). Graduate Theses, Dissertations, and Problem Reports. 8890.