Layer-dependent ferroelectricity in 2H-stacked few-layer α-In₂Se₃

Abstract

Atomically thin two-dimensional (2D) van der Waals materials have exhibited many exotic layer-dependent physical properties including electronic structure, magnetic order, etc. Here, we report a striking even-odd layer dependent oscillation...

Control of photocurrent and multi-state memory by polar order engineering in 2H-stacked α-In2Se3 ferroelectric

“…1c and Fig. S2 show the clear IP and OOP PFM phase contrast after writing two square patterns by applying ±5 V direct current (DC) tip bias consecutively, indicating the polarization reversal and interlocked ferroelectricity [16,17]. The same results also exist in a 19-nm-thick 2H α-In 2 Se 3 (Fig.…”

“…At present, emerging 2D van der Waals (vdW) ferroelectrics may avert the above issues and enable nondestructive data reading and indefatigable data writing, thanks to their clean vdW interfaces and narrow-band-gap nature [12]. Among the known 2D vdW ferroelectric semiconductors, α-In 2 Se 3 possesses robust room-temperature ferroelectricity even down to the monolayer limit, and large-area samples can be grown using simple and low-cost preparation methods [14][15][16]. Moreover, the α-In 2 Se 3 ferroelectric has two different stacking constructions, namely hexagonal (2H) and rhombohedral (3R) structures [17][18][19].…”

“…Moreover, the α-In 2 Se 3 ferroelectric has two different stacking constructions, namely hexagonal (2H) and rhombohedral (3R) structures [17][18][19]. Although both of them have some similar properties such as the interlocked in-plane (IP) and out-of-plane (OOP) ferroelectricity [17,[20][21][22][23], mechanical flexibility [24,25] and bandgap tunability [2,26], pristine 2H α-In 2 Se 3 shows a distinctive polarization arrangement, that is, the interlayer IP polarization is alternately anti-parallelly aligned [16]. This special polar order configuration can bring striking physical properties, such as layer-dependent IP phase contrast and polarization [16,20].…”

Multifunctional Optoelectronic Synapse Based on Ferroelectric Van der Waals Heterostructure for Emulating the Entire Human Visual System

“…[34] According to the literature, IP ferroelectricity is thought to play a dominant role in this case. [35] In contrast, in this study, α-In 2 Se 3 was transferred after the electrodes were prepared in order to form vdW contacts. The currents in stages 2 and 3 of the hysteresis loops are higher than those in stages 1 and 4 (Figure S5, Supporting Information, and Figure 5a).…”

Nondestructive Picosecond Ultrasonic Probing of Intralayer and van der Waals Interlayer Bonding in α‐ and β‐In2Se3

“…The α‐phase is ferroelectric with different ferroelectric properties for hexagonal (2H) and rhombohedral (3R) structures with AB and ABC stacking of the individual quintuple layer, respectively. [ 17–25 ] On the other hand, β‐In 2 Se 3 (3R) is not ferroelectric and can emerge under thermal annealing of α‐In 2 Se 3 . [ 26,27 ] Furthermore, superconductivity was reported in β‐In 2 Se 3 under high pressure due to phonon softening.…”