Noriaki Terakubo

Electrical and mechanical properties of piezoelectric ceramic/metal composites in the Pb(Zr, Ti)O3/Pt system

As a model for composite materials of piezoelectric ceramic and metal, lead zirconate titanate (PZT) and platinum (Pt) particulate composites were fabricated by power processing. The electrical and mechanical properties of the PZT–Pt composites were measured as a function of the Pt volume fraction. The relative dielectric constants of the PZT–Pt composites increased markedly, while the piezoelectric constants and electromechanical coupling coefficients decreased with increasing Pt content. When the Pt volume fraction exceeded 30%, the PZT–Pt composite became electrically conductive because of percolation of the Pt particles. The Pt-dispersed PZT composites enhanced the mechanical properties, particularly the high fracture resistance, compared to the monolithic PZT ceramics.

Band Structures of Perovskite-Like Fluorides for Vacuum-Ultraviolet-Transparent Lens Materials

In the semiconductor industry, perovskite-like fluorides that have wide band gaps are potential candidates for vacuum-ultraviolet-transparent lens materials in optical lithography steppers. KMgF3 and BaLiF3 single crystals have already been grown, but materials with wider band gaps are desired. To find compositions more effective than KMgF3 and BaLiF3, we performed local density approximation (LDA) based ab initio band calculations for perovskite-like fluorides ABF3, where A and B include an exhaustive list of alkali metals, alkaline-earth metals, and other selected elements. We found that LiBeF3, NaBeF3, KBeF3, and RbMgF3 may have wider indirect band gaps than KMgF3 does. We also found that SrLiF3 may have a wider direct band gap than BaLiF3 does.

Band-Structure Design of Fluoride Complex Materials for Deep-Ultraviolet Light-Emitting Diodes

The design principle for fluoride-containing optical devices for applications in the deep ultraviolet range is discussed. Variations in band gap energy, band structure and lattice constant of LiBaxCaySr(1-x-y)F3 and Li(1-x)KxBa(1-y)MgyF3 have been studied. The band structure and transition type of these fluorides are predicted by ab initio band calculations based on the local density approximation. The lattice-matched double-hetero structure of direct-band-gap compounds LiBaxCaySr(1-x-y)F3 on LiSrF3 and Li(1-x)KxBa(1-y)MgyF3 on either LiBaF3 or KMgF3 is sufficiently feasible to fabricate.

Design Proposal of Light Emitting Diode in Vacuum Ultraviolet Based on Perovskite-Like Fluoride Crystals

The variation of band gap energy, band structure and lattice constant of mixed LiBaF3, LiCaF3 and LiSrF3 perovskites is studied. The band structure and transition type of these fluorides is predicted by ab initio band calculation based on the local density approximation. The design principle of vacuum ultraviolet light emitting diode is proposed. The lattice-matched double-hetero structure of different perovskite-like fluorides is found to be sufficiently feasible to fabricate with direct-band-gap compounds LiBaxCaySr(1-x-y)F3 on LiSrF3.

Design of wide-gap fluoride heterostructures for deep ultraviolet optical devices

The design of fluoride-based optical devices for deep ultraviolet applications is discussed. Variations in the band-gap energy and band structure with respect to composition are investigated for Li(1−x)KxBa(1−y)MgyF3 perovskites. The band-gap energy, lattice constant, and band structure of perovskitelike fluorides are estimated based on ab initio calculations within the local-density approximation. The lattice-matched double heterostructure with direct band-gap compounds (Li(1−x)KxBa(1−y)MgyF3 on either LiBaF3 or KMgF3 substrates) is promising for fabrication.

Ab Initio Study of Divalent

Divalent 3d transition metal impurities (V, Cr, Mn, Fe, Co, Ni, and Cu) in KMgF3 and BaLiF3 have been investigated by local-spin-density approximation (LSDA)-based ab initio calculations using an ultrasoft pseudopotential method and a planewave basis set. The results of numerical calculations show that the 3d transition metal impurities exhibit mid-gap levels and that the electronic transition from impurity levels to the conduction band results from the absorption of vacuum ultraviolet (VUV) light with energy lower than band-gap width. Therefore, 3d transition metal contaminations in KMgF3 and BaLiF3 should be avoided for VUV lithographic lens applications.

3d

The variation of band gap energy and band structure with respect to composition of Li/sub (1-x)/K/sub x/Ba/sub (1-y)/Mg/sub y/F/sub 3/ perovskite-like fluorides is investigated. Analysis of energy chart shows the feasibility of fabricating Li/sub (1-x)/K/sub x/Ba/sub (1-y)/Mg/sub y/F/sub 3/ on either LiBaF/sub 3/ or KMgF/sub 3/.