Terahertz Emission from Tubular Pb(Zr,Ti)O₃Nanostructures

Abstract

We report intense terahertz emission from lead zirconate titanate (PZT) tubular nanostructures, which have a wall thickness around 40 nm and protrude on n-type Si substrates. Such emission is totally absent in flat PZT films or bulk; hence the effect is attributed to the nanoscale geometry of the tubes. The terahertz radiation is emitted within 0.2 ps, and the spectrum exhibits a broad peak from 2 to 8 THz. This is a gap in the frequency spectrum of conventional semiconductor terahertz devices, such as ZnTe, and an order of magnitude higher frequency peak than that in the well-studied p-InAs, due to the abnormally large carrier concentration gradient in the nanostructured PZT. The inferred mechanism is optical rectification within a surface accumulation layer, rather than the Dember effect. The terahertz emission is optically pumped, but since the tubes exhibit ferroelectric switching, electrically driven emission may also be possible. EPR reveals 02 molecules adsorbed onto the nanotubes, which may play some role in the emission.

Room-temperature single phase multiferroic magnetoelectrics: Pb(Fe, M)x(Zr,Ti)(1−x)O3 [M = Ta, Nb]

“…The low electrical conductivity of these materials thus produced a good alternative to BiFeO 3 for commercial device materials with intended embodiments as multiferroic memories, 18-21 sensors, 22 or voltage-controlled magnetic tunnel junctions [23][24][25] or THz generators. [26][27][28] Of the members of this family of quaternary B-site perovskites, the Fe/W/Zr/Ti compounds exhibit only biquadratic coupling between polarization (P) and magnetization (M), and not linear magnetoelectricity. However, the remarkable dependence of electrically switched polarization P upon dc magnetic field H (vanishing above H ¼ 0.9 T) due to magnetically dependent relaxation times 29 may still permit some practical devices.…”

Radiative recombination and other processes related to excess charge carriers, decisive for efficient performance of electronic devices

“…These materials were a subject of our common studies with prof. Arūnas Krotkus from the Semiconductor Physics Institute in Vilnius, Lithuania, who in the last twenty years has performed the prominent research of a broad spectrum of semiconductor materials with a short excess carrier lifetime and showed their high usefulness in ultrafast optoelectronic devices, like THz emitters or THz detectors (see [19][20][21][22][23][24][25][26][27][28][29] for some of the most prominent results of A. Krotkus).…”

Ferroelectric nanoparticles, wires and tubes: synthesis, characterisation and applications

“…They attributed this effect to the 40 vertical alignment of the nanotubes. 101 Hong et al 134 noticed a five times enhancement in the piezoelectric response for PVDFTrFE nanostructures aligned perpendicular on a Si substrate compared to PVDF-TrFE thin films. 3D nanostructuring also provides an opportunity to study the size and morphology 45 dependence of ferroelectric characteristics.…”