HfO 2 -based antiferroelectric-like thin films are increasingly being considered for commercial devices. However, even with initial promise, the temperature sensitivity of electrical properties such as loss tangent and leakage current remains unreported. 50 nm thick, 4 at. % Al-doped HfO 2 thin films were synthesized via atomic layer deposition with both top and bottom electrodes being TiN or Pt. A study of their capacitance vs temperature showed that the Pt/Al:HfO 2 /Pt had a relative dielectric permittivity of 23.30 ± 0.06 at room temperature with a temperature coefficient of capacitance (TCC) of 78 ± 86 ppm/°C, while the TiN/Al:HfO 2 /TiN had a relative dielectric permittivity of 32.28 ± 0.14 at room temperature with a TCC of 322 ± 41 ppm/°C. The capacitance of both devices varied less than 6% over 1 to 1000 kHz from −125 to 125 °C. Both capacitors maintained loss tangents under 0.03 and leakage current densities of 10 −9 –10 −7 A/cm 2 between −125 and 125 °C. The TiN/Al:HfO 2 /TiN capacitor maintained an energy storage density (ESD) of 18.17 ± 0.79 J/cm 3 at an efficiency of 51.79% ± 2.75% over the −125 to 125 °C range. The Pt/Al:HfO 2 /Pt capacitor also maintained a stable ESD of 9.83 ± 0.26 J/cm 3 with an efficiency of 62.87% ± 3.00% over the same temperature range. Suchmore »
Bulk-like dielectric and magnetic properties of sub 100 nm thick single crystal Cr2O3 films on an epitaxial oxide electrode
Abstract The manipulation of antiferromagnetic order in magnetoelectric Cr 2 O 3 using electric field has been of great interest due to its potential in low-power electronics. The substantial leakage and low dielectric breakdown observed in twinned Cr 2 O 3 thin films, however, hinders its development in energy efficient spintronics. To compensate, large film thicknesses (250 nm or greater) have been employed at the expense of device scalability. Recently, epitaxial V 2 O 3 thin film electrodes have been used to eliminate twin boundaries and significantly reduce the leakage of 300 nm thick single crystal films. Here we report the electrical endurance and magnetic properties of thin (less than 100 nm) single crystal Cr 2 O 3 films on epitaxial V 2 O 3 buffered Al 2 O 3 (0001) single crystal substrates. The growth of Cr 2 O 3 on isostructural V 2 O 3 thin film electrodes helps eliminate the existence of twin domains in Cr 2 O 3 films, therefore significantly reducing leakage current and increasing dielectric breakdown. 60 nm thick Cr 2 O 3 films show bulk-like resistivity (~ 10 12 Ω cm) with a breakdown voltage in the range of 150–300 MV/m. Exchange bias measurements of 30 nm thick Cr 2 more »
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