Emergence of room-temperature ferroelectricity at reduced dimensions

Abstract

The enhancement of the functional properties of materials at reduced dimensions is crucial for continuous advancements in nanoelectronic applications. Here, we report that the scale reduction leads to the emergence of an important functional property, ferroelectricity, challenging the long-standing notion that ferroelectricity is inevitably suppressed at the scale of a few nanometers. A combination of theoretical calculations, electrical measurements, and structural analyses provides evidence of room-temperature ferroelectricity in strain-free epitaxial nanometer-thick films of otherwise nonferroelectric strontium titanate (SrTiO3). We show that electrically induced alignment of naturally existing polar nanoregions is responsible for the appearance of a stable net ferroelectric polarization in these films. This finding can be useful for the development of low-dimensional material systems with enhanced functional properties relevant to emerging nanoelectronic devices.

Воздействие механических напряжений на зарядовое состояние межфазной границы в гетероструктурах LaAlO-=SUB=-3-=/SUB=-/(001)SrTiO-=SUB=-3-=/SUB=- c нарушенной стехиометрией

“…Привнесенное механическими напряжениями искажение элементарных ячеек в прослойке титаната стронция, прилегающей к межфазной границе, обус-ловливает появление в ней спонтанной поляризации, вектор которой направлен перпендикулярно плоскости подложки. Особенности формирования сегнетоэлектри-ческой фазы в наноразмерных пленках STO активно обсуждаются в настоящее время в литературе [13,14]. При высокой концентрации вакансий кислорода в под-ложке и существенной концентрации атомов лантана в приграничном слое подложки одновременно с появле-нием спонтанной поляризации в прослойке подложки у межфазной границы возникает деполяризующее поле, Физика твердого тела, 2018, том 60, вып.…”

Anomalous ferroelectric switching dynamics in single crystalline SrTiO3

“…But whether such a scenario should manifest itself in the switching mechanism which involves nucleation and growth of favorable domains or the coherent rotation of the polar domains remains unclear. On the other hand, a recent experiment by Lee et al 26 used naturally existing polar nanoregions formed due to local nanoscale inhomogeneities such as Sr vacancies to stabilize a net switchable polarization in nanometer thick epitaxial, strain free SrTiO 3 film. The EDS study carried out by us also reveals Sr deficiencies at nanoscale.…”

“…Whether these nanoclusters can give rise to net macroscopic electric polarization is still an open question. Very recently, however, Lee et al have come out with evidence that alignment and stabilization of these polar nanoregions in ultra-thin SrT iO 3 film is indeed possible under electric field which can result in net ferroelectric polarization at room temperature 26 although the dynamics of the switching process is not elaborated. Interestingly, majority of the experiments on SrT iO 3 have been carried out without using any electrode material which does not help establish a holistic insight into the subject since the electrical boundary conditions at the interface influence the ferroelectric phase.…”

Recent developments related to multifunctional ferroelectric for room-temperature applications

“…Recent publications have reported important approaches of bulk and nanostructure ferroelectric materials at room temperature [1][2][3][4][5] Magnetoelectric multiferroic materials enable fast electrical writing and magnetic reading, and can thus be applied to non-volatile random access memory. However, fast electrical writing and magnetic reading exist more difficulties in single crystalline structure bulk materials because ferroelectricity need closed-shell d 0 or s 2 cation and ferromagnetic need open-shell d n with unpaired electron.…”

“…By DFT calculations and experimental measurements, they found that the local structures conducting polar nanodomains at room-temperature are embedded in insulating domain boundaries, which can form "nanocapacitor" domains. The stable capacitance offers "nanobits," which have potential applications in high-density information storage at room temperature.Ferroelectric materials have important nanoelectronic applications at room temperature [3]. Many researchers have demonstrated that nanostructures will enhance the performance of nanodevices [2][3][4].…”