Room-temperature ferroelectricity in strained SrTiO3

Abstract

Systems with a ferroelectric to paraelectric transition in the vicinity of room temperature are useful for devices. Adjusting the ferroelectric transition temperature (T(c)) is traditionally accomplished by chemical substitution-as in Ba(x)Sr(1-x)TiO(3), the material widely investigated for microwave devices in which the dielectric constant (epsilon(r)) at GHz frequencies is tuned by applying a quasi-static electric field. Heterogeneity associated with chemical substitution in such films, however, can broaden this phase transition by hundreds of degrees, which is detrimental to tunability and microwave device performance. An alternative way to adjust T(c) in ferroelectric films is strain. Here we show that epitaxial strain from a newly developed substrate can be harnessed to increase T(c) by hundreds of degrees and produce room-temperature ferroelectricity in strontium titanate, a material that is not normally ferroelectric at any temperature. This strain-induced enhancement in T(c) is the largest ever reported. Spatially resolved images of the local polarization state reveal a uniformity that far exceeds films tailored by chemical substitution. The high epsilon(r) at room temperature in these films (nearly 7,000 at 10 GHz) and its sharp dependence on electric field are promising for device applications.

Strain-Engineered Oxygen Vacancies in CaMnO3 Thin Films

“…Recent examples of such strain-functionality coupling include the control of metal-to-insulator transition temperature in VO2 5 and the insulator-tosuperconductor transition temperature in La1.9Sr0.1CuO4 6 . Going beyond the ability to effectively manipulate already existing physical properties of a given material, strain has also been shown to invoke entirely new exotic ground states such as ferroelectricity in SrTiO3 and increased ferroelectric polarization in BaTiO3, consistent with theoretical predictions [7][8][9] .…”

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

“…Появление отличной от нуля P S в кристаллах титаната стронция может быть индуцировано механическими напряжения-ми [10], нарушением стехиометрии [11] и электрическим полем [12]. Параметр элементарной ячейки алюмината лантана (∼ 3.789 ¦ ) существенно меньше соответству-ющего параметра титаната стронция (∼ 3.905 ¦ ) [1].…”

“…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.…”

Electronic structure and magnetic symmetry in MnTiO3analyzed by second harmonic generation

“…Therefore, they are highly beneficial in understanding the physics behind the coupling of these coexisting orders, such as in magneto-electric coupling. It has also been reported that these materials are important for technological applications such as memory devices and solar cells [3][4][5][6][7][8][9][10][11] . Antiferromagnetic MnTiO 3 (T N = 64 K), exhibiting ilmenite structure, possesses a magnetic field induced spin-flop phase (H c = 6.5 T), and it further exhibits a linear magnetoelectric (ME) effect [12][13][14] .…”