incompatibilities with silicon and modern semiconductor processes. [5] Since the discovery of ferroelectricity in HfO 2 -based thin films in 2011, [6] fluorite-structure binary oxides have attracted considerable interest as they are compatible with complementary metal-oxide-semiconductor (CMOS) processes. [7] Accordingly, HfO 2based ferroelectric memory has received significant attention in recent years, [1,8,9] primarily focused on charge-based ferroelectric random access memory (FeRAM) and ferroelectric field effect transistors (FeFETs). [2,10] Meanwhile, resistiveswitching materials-which exhibit electrically-induced resistance changes in metal-dielectric-metal junctions or heterostructures with multi-dielectric barriershave emerged as promising candidates for novel beyond-CMOS data-centric computing paradigms. [11][12][13] In this context, ferroelectric tunnel junctions (FTJs) present a promising energy-efficient resistive switching memory [12,13] as FTJs exploit the ferroic polarization functionality of the insulating barrier. [14] Voltage-controlled polarization-dependent tunneling through the ferroelectric layer (tunnel electroresistance, TER) can yield much larger ON/OFF conductance ratios [15,16] than, for example, current-controlled magnetic tunnel junctions, [12] another two-terminal tunneling resistive switching device.A critical requirement for FTJs is to achieve a sufficiently high tunneling current (J ON ) at the ON state to ensure that a scaled device can be read rapidly, while still exhibiting a large TER ((J ON -J OFF )/J OFF × 100%). [13] Considering the large band gap of HfO 2 (≈6 eV), the thickness of HfO 2 in the FTJ will need to be reduced to the ultrathin limit for adequate tunnel current. Tunnel junctions implementing CMOS-compatible HfO 2 -based ferroelectric barriers have been recently demonstrated, [17][18][19] but even three nanometer Zr-doped HfO 2 (Zr:HfO 2 ) barriers were found to be too thick to obtain nano-ampere level current in micron-sized capacitors. [20] Therefore, high ON current is a critical consideration; however, the increased ON state current from an ultrathin barrier will coincide with an increased OFF state current. For array-level implementations, where sneak leakage paths can lead to increased power consumption, selector devices may be required in conjunction with the FTJ memory elements to reduce such sneak currents. [13] Here, we demonstrate FTJs utilizing one nanometer Zr:HfO 2 as the ferroelectric barrier, grown by atomic layer deposition (ALD) directly on silicon, thereby scaling down the tunnel barrier ABSTRACT: In ferroelectric materials, spontaneous symmetry breaking leads to a switch-able electric polarization, which offers significant promise for nonvolatile memories. In particular, ferroelectric tunnel junctions (FTJs) have emerged as a new resistive switching memory which exploits polarizationdependent tunnel current across a thin ferroelectric barrier. This work integrates FTJs with com-plementary metal-oxide-semiconductor-compatible Zr-doped HfO 2 (Zr...