Optical and mechanical properties of MgO crystals implanted with lithium ions

Abstract

Defect profile induced by implantation of Li+ ions with an energy of 175 keV and a fluence of 1×1017 ions/cm2 in MgO single crystals was characterized by Rutherford backscattering and optical absorption measurements. Several absorption bands at 5.0, 3.49, 2.16, and 1.27 eV, identical to those found in neutron irradiated crystals, were observed and have been previously associated with oxygen vacancies and higher-order point defects involving oxygen vacancies. Despite the high fluence of Li+ ions, no evidence was found for the formation of Li nanocolloids during implantation. Nanoindentation experiments demonstrated that both the hardness and Young’s modulus were higher in the implanted layer than in the sample before implantation. The maximum values were H=(17.4±0.4) and E=(358±9) GPa, respectively, at a contact depth of ≈165 nm. Thermal annealings in flowing argon at increasing temperatures improved the crystalline quality of the implanted layer. After annealing at 500 K, two extinction bands at ≈2.75 and 3.80 eV emerged. These bands are attributed to Mie scattering from metallic lithium nanocolloids with either a face-centered- or a body-centered-cubic structure. The latter band was almost absent by 950 K. The former reached a maximum intensity after the thermal treatment at 1050 K and disappeared by 1250 K. The behavior of these bands can be satisfactorily explained by the Maxwell–Garnett theory. The decrease in hardening cannot be correlated with the thermal destruction of the absorption bands at 5.0, 3.49, 2.16, and 1.27 eV, but rather with the annihilation of both lithium and oxygen interstitials. Lithium outdiffusion from the implanted region takes place at temperatures of ≈1100 K. It is concluded that the hardening observed in the implanted region was primarily due to the extraordinarily large concentration of both lithium and oxygen interstitials.

Subsurface synthesis and characterization of Ag nanoparticles embedded in MgO

“…Metallic nanoparticles embedded in various dielectric materials have generated considerable interest in the fields of opto-electronics and nonlinear optics due to their strong coupling to incident electromagnetic fields [1][2][3][4][5][6][7][8][9][10][11]. The optical response of these substrates is dominated by the localized surface plasmon resonance (LSPR), which leads to an electric field enhancement that can be used to boost molecular optical responses such as surface-enhanced Raman scattering (SERS) [12].…”

Growth and properties of highly oriented lead-free Mn-doped NaNbO3–BaTiO3 piezoelectric thin films prepared by chemical solution deposition

“…The Pt bottom electrodes had the same 200 nm-thick. The thickness and Young's modulus of the used substrates were 500 mm and 160 GPa [20] for Si, and 1 mm and 280 GPa [21] for MgO(1 0 0). Therefore, the effective piezoelectric constant of the current (1 0 0)-oriented NN-BT thin films might be lowered due to the clumping effect, which is caused by the physical characteristics of the substrate.…”