Argyrodites with a general chemical formula of A 8 BX 6 (A = Cu, Ag; B = Si, Ge, Sn; and X = S, Se, and Te) are known for the intimate interplay among mobile ions, electrons, and phonons, which yields rich material physics and materials chemistry phenomena. In particular, the coexistence of fast ionic conduction and promising thermoelectric performance in

In the quest for reliable and power-efficient memristive devices, ferroelectric tunnel junctions are being investigated as potential candidates. Complementary metal oxide semiconductor-compatible ferroelectric hafnium oxides are at the forefront. However, in epitaxial tunnel devices with thicknesses around ≈4−6 nm, the relatively high tunnel energy barrier produces a large resistance that challenges their implementation. Here, we show that ferroelectric and electroresistive switching can be observed in ultrathin 2 nm epitaxial Hf 0.5 Zr 0.5 O 2 (HZO) tunnel junctions in large area capacitors (≈300 μm 2 ). We observe that the resistance area product is reduced to about 160 and 65 Ω•cm 2 for OFF and ON resistance states, respectively. These values are 2 orders of magnitude smaller than those obtained in equivalent 5 nm HZO tunnel devices while preserving a similar OFF/ON resistance ratio (210%). The devices show memristive and spike-timing-dependent plasticity behavior and good retention. Electroresistance and ferroelectric loops closely coincide, signaling ferroelectric switching as a driving mechanism for resistance change.

Systematic studies on polycrystalline Hf1-xZrxO2 films varying Zr content show that HfO2 films are paraelectric (monoclinic). If Zr content is increased films become ferroelectric (orthorhombic) and after antiferroelectric (tetragonal). Whereas HfO2 shows very good insulating properties and it is used in metaloxide-semiconductor field-effect devices, ZrO2 shows good piezoelectric properties, but it is antiferroelectric. In between, Hf0.5Zr0.5O2 shows good ferroelectric properties at expenses of poorer insulating and piezoelectric properties than HfO2 and ZrO2, respectively. Here, we explore ferroelectric, insulating and piezoelectric properties of a series of epitaxial films of Hf1-xZrxO2 with different composition. We show that epitaxial growth enhances the stabilization of the ferroelectric behaviour compared with polycrystalline films in a wider compositional range and up to around 1000 K. This allows, in epitaxial ZrO2 films ferroelectricity coexists with better piezoelectric and insulating properties than Hf0.5Zr0.5O2 and in HfO2 epitaxial films ferroelectricity coexists with better insulating properties than Hf0.5Zr0.5O2. In both cases, the ferroelectric endurance is poorer than for Hf0.5Zr0.5O2.

The metastable orthorhombic phase of Hf0.5Zr0.5O2 (HZO) can be stabilized in thin films on La0.67Sr0.33MnO3 (LSMO) buffered (001)-oriented SrTiO3 (STO) by an intriguing epitaxy that results in (111)-HZO oriented growth...

In the quest for energy efficient and fast memory elements, optically controlled ferroelectric memories are promising candidates. Here, we show that, by taking advantage of the imprint electric field existing in the nanometric BaTiO3 films and their photovoltaic response at visible light, the polarization of suitably written domains can be reversed under illumination. We exploit this effect to trigger and measure the associate change of resistance in tunnel devices. We show that engineering the device structure by inserting an auxiliary dielectric layer, the electroresistance increases by a factor near 2 × 103%, and a robust electric and optic cycling of the device can be obtained mimicking the operation of a memory device under dual control of light and electric fields.