Control of surface potential at polar domain walls in a nonpolar oxide

Abstract

International audienceFerroic domain walls could play an important role in microelectronics, given their nanometric size and often distinct functional properties. Until now, devices and device concepts were mostly based on mobile domain walls in ferromagnetic and ferroelectric materials. A less explored path is to make use of polar domain walls in nonpolar ferroelastic materials. Indeed, while the polar character of ferroelastic domain walls has been demonstrated, polarization control has been elusive. Here, we report evidence for the electrostatic signature of the domain-wall polarization in nonpolar calcium titanate (CaTiO 3). Macroscopic mechanical resonances excited by an ac electric field are observed as a signature of a piezoelectric response caused by polar walls. On the microscopic scale, the polarization in domain walls modifies the local surface potential of the sample. Through imaging of surface potential variations, we show that the potential at the domain wall can be controlled by electron injection. This could enable devices based on nondestructive information readout of surface potential

Electrically driven ferroelastic domain walls, domain wall interactions, and moving needle domains

“…The first example was CaTiO 3 [19] where polarity was observed in transmission electron microscopy. This observation was further confirmed by other techniques, such as second harmonic generation (SHG) [20,23,26,27]. Polarity was also predicted on theoretical grounds [24].…”

“…Moreover, the collective response of such ferroelastic domain patterns displays hallmarks for a glassy behavior as in case of low temperature relaxations during friction experiments [46] with similarities to patterns in magnetic spiral systems [63]. The main issue is whether these very sensitive reactions to external forcing or the interaction between domains in the ferroelastic phase are purely elastic in nature or whether wall polarity plays a role [23,32,64,65].…”

“…These switches are largely athermal because the energy barriers between different domain states are usually much greater than the thermal energy. It was shown that ferroelastic domain boundaries are generally polar [19][20][21][22][23][24][25]. The first example was CaTiO 3 [19] where polarity was observed in transmission electron microscopy.…”

Interaction of low-energy electrons with surface polarity near ferroelastic domain boundaries

“…Experimentally, the intersection of twin boundaries with the surface of CaTiO 3 was studied by low-energy electron microscopy (LEEM) [30]. This technique provides full-field, noncontact imaging of surface potential with a spatial resolution better than 20 nm [31].…”

A Ferroelastic Film at the Edge of Chaos

“…Recent work [69][70][71] shows that, during the ferroelectic phase transition at 120°C, BaTiO 3 crystals display transient intersections between polar ferroelastic or ferroelectric 90°w alls and the (001) surface that are electrically charged and is also shown to take place as the temperature decreases from (i) 80°C to (ii) 60°C and to (iii) 25°C. Domain notation is as follows: a 1 ¼ ðP 0 ; 0; 0Þ, a 2 ¼ ð0; P 0 ; 0Þ, c ¼ ð0; 0; P 0 Þ, O 1þ ¼ ðP 0 ; P 0 ; 0Þ, O 1− ¼ ð−P 0 ; −P 0 ; 0Þ, O 2þ ¼ ðP 0 ; −P 0 ; 0Þ, O 2− ¼ ð−P 0 ; P 0 ; 0Þ, O 4þ ¼ ðP 0 ; 0; −P 0 Þ, O 5þ ¼ ð0; P 0 ; P 0 Þ, O 5− ¼ ð0; −P 0 ; −P 0 Þ, O 6þ ¼ ð0; P 0 ; −P 0 Þ, O 6− ¼ ð0; −P 0 ; P 0 Þ, and R 1 ¼ ðP 0 ; −P 0 ; −P 0 Þ.…”