Photochemistry on a polarisable semi-conductor: what do we understand today?

Abstract

The continued development of ferroelectric materials into more and more consumer led applications has been at the forefront of recent ferroelectric material research. It is, however, possible to view a ferroelectric as a wide band gap semi-conductor that can sustain a surface charge density. This charge density arises from the movement of ions in the crystal lattice and the need to compensate for this charge. When viewing ferroelectrics as polarisable semi-conductors a large number of new interactions are possible. One such is the use of super band gap illumination to generate electron-hole pairs. These photogenerated carriers can then perform local electrochemistry.

Influence of annealing on the photodeposition of silver on periodically poled lithium niobate

“…3,5,6 Polarizationdependent surface reactivity has been exploited extensively for the photoreduction of metallic nanoparticles. [1][2][3][4] Typically, when aqueous AgNO 3 solution is placed on a ferroelectric surface illuminated with super bandgap light, photogenerated electrons accumulate at the positive domain surface due to downwards band bending, leading to the deposition of Ag particles on the positive domains via the reduction of Ag þ to Ag 0 .…”

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

“…Among the possible alternatives to TiO 2 , polar materials have recently attracted significant interest because their surface dipoles can react easily with charged species and supply built-in electric potentials to increase the carrier mobility [6,7]. However, control of the surface reactivity of these materials is difficult [8], e.g., because exposed surface dipoles often cause undesired atomic or electronic reconstructions and unexpected adsorption of charged species which can interfere with the reaction of interest [9][10][11]. Less well known than TiO 2 and polar semiconductors are heterostructures composed of stable TiO 2 thin films supported by a ferroelectric substrate [12,13].…”

Direct shape control of photoreduced nanostructures on proton exchanged ferroelectric templates

“…This leads to the reduction of Ag þ to Ag 0 where the electrons accumulate, allowing for the fabrication of silver nanostructures on specified regions, i.e., positive or negative domains, and along domain walls or chemically patterned interfaces, depending on the deposition conditions and the sample properties. [5][6][7][8][9][10][11][12][13][14][15][16] Congruent lithium niobate (LN) is one of the most studied ferroelectric crystals due to its large electro-optic and electro-mechanical coupling coefficients and has been used extensively for photodeposition studies. 4,5,[11][12][13]16 Illuminating LN with UV light of energies higher than the bandgap (E g $ 3.9 eV, which corresponds to a wavelength of k < 318 nm) 17 allows the photogeneration of electron-hole pairs that can participate in reduction and oxidation reactions.…”

“…4,5,[11][12][13]16 Illuminating LN with UV light of energies higher than the bandgap (E g $ 3.9 eV, which corresponds to a wavelength of k < 318 nm) 17 allows the photogeneration of electron-hole pairs that can participate in reduction and oxidation reactions. 10 When photochemical reactions have been employed to fabricate silver nanowires on a domain patterned ferroelectric template, i.e., periodically poled lithium niobate (PPLN), the nanostructures are confined to the 180 domain walls. 11,14 The location of the nanowires can be controlled by varying the domain pattern configurations, which requires electric field poling.…”