포항공과대학교 · Engineering
알레르자 카시르 교수의 연구실은 허피아 기반 페로일렉트릭 및 안티페로일렉트릭 산화물 박막의 물성 제어를 핵심으로 하며, 특히 HfO₂–ZrO₂계 페로일렉트릭 박막의 잔류 극화도 향상과 웨이크업 효과 억제를 위한 공정 조절 기법을 개발하고 있습니다. 고해상도 구조 분석과 전기적 특성 측정을 통합하여 모트로피크 상변화 경계(MPB)의 존재와 그가 유도하는 높은 유전율 및 피에조전기 특성을 규명하고 있으며, 실리콘 기반 반도체 소자에 적합한 박막 소재의 설계 원리를 제시하고 있습니다. 특히 오존 펄스 조절, 캡핑 전극 설계, 나노다층막 구조 최적화를 통해 기계적·열적 스트레인과 결함 농도를 제어하는 혁신적 접근을 펼치고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
A wake-up free Hf0.5Zr0.5O2 (HZO) ferroelectric film with the highest remnant polarization (Pr) value to date was achieved through tuning of the ozone pulse duration, the annealing process, and the metal/insulator interface. The ozone dosage during the atomic layer deposition of HZO films appears to be a crucial parameter in suppressing the mechanisms driving the wake-up effect. A tungsten capping electrode with a relatively low thermal expansion coefficient enables the induction of an in-plane
Wake‐up effect is still an obstacle in the commercialization of hafnia‐based ferroelectric thin films. Herein, the effect of defects, controlled by ozone dosage, on the field cycling behavior of the atomic layer deposited Hf 0.5 Zr 0.5 O 2 (HZO) films is investigated. A nearly wake‐up free device is achieved after reduction of carbon contamination and oxygen defects by increasing the ozone dosage. The sample which is grown at 30 s ozone pulse duration shows about 97% of the woken‐up P r at the p
The existence of a morphotropic phase boundary (MPB) inside HfO<sub>2</sub>-ZrO<sub>2</sub> solid solution thin films has been predicted; if it exists, it provides a new path toward an ideal silicon-compatible dielectric. Herein, we investigate the structural evolution along with the dielectric and ferroelectric behaviors of differently designed HfO<sub>2</sub>-ZrO<sub>2</sub> thin films to engineer the density of the MPB inside the film structure and consequently, enhance the dielectric propert
Recently, based on the phase‐field modeling, it is predicted that Hf 1‐ x Zr x O 2 (HZO) exhibits the morphotropic phase boundary (MPB) in its compositional phase diagram. Herein, the effect of structural changes between tetragonal (t) and orthorhombic (o) phases on the ferroelectric (FE) and dielectric properties of HZO films is investigated to probe the existence of MPB region. The structural analysis shows that by adjusting the ozone dosage during the atomic layer deposition process and annea
Engineering of HfO2–ZrO2 ferroelectric thin films can substantially increase their dielectric constant. Here, we investigate dielectric and structural properties of ∼10 nm thin films consisting of stacked 1 nm thin ferroelectric (FE) Hf1–xZrxO2 (HZO(x)) and antiferroelectric (AFE) ZrO2 layers. At x < 0.5, the measurements of polarization vs electric field revealed pure FE hysteresis loops, whereas at x > 0.5, pinched hysteresis loops with some remnant polarization were observed, which indicate a
Morphotropic phase boundaries (MPBs) show substantial piezoelectric and dielectric responses, which have practical applications. The predicted existence of MPB in HfO<sub>2</sub>-ZrO<sub>2</sub>solid solution thin film has provided a new way to increase the dielectric properties of a silicon-compatible device. Here, we present a new fabrication design by which the density of MPBρMPBand consequently the dielectric constant<i>ϵ</i><sub>r</sub>of HfO<sub>2</sub>-ZrO<sub>2</sub>thin film was conside
In this paper, we propose a method to improve the performance of TiN/Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> (HZO)/TiN Nano-capacitors used in memory devices. Instead of direct fabrication of the TiN/HZO/TiN device, our method involves an intermediate step in which W metal is used as a capping material to induce a large in-plane tensile strain during rapid thermal annealing, resulting in a total suppression of the monoclinic phase and the appearance of the ferroelectric phase. Consequently
A large coercive field<i>E</i><sub>C</sub>of HfO<sub>2</sub>based ferroelectric devices poses critical performance issues in their applications as ferroelectric memories and ferroelectric field effect transistors. A new design to reduce<i>E</i><sub>C</sub>by fabricating nanolaminate Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub>/ZrO<sub>2</sub>(HZZ) thin films is used, followed by an ensuing annealing process at a comparatively high temperature 700 °C. High-resolution electron microscopy imaging
Recently, based on the phase-field modeling, it was predicted that Hf1-xZrxO2 (HZO) exhibits the morphotropic phase boundary (MPB) in its compositional phase diagram. Here, we investigate the effect of structural changes between tetragonal (t) and orthorhombic (o) phases on the ferroelectric and dielectric properties of HZO films to probe the existence of MPB region. The structural analysis show that by adjusting the ozone dosage during the atomic layer deposition process and annealing condition
NiO thin films with various strains were grown on SrTiO<sub>3</sub>(STO) and MgO substrates using a pulsed laser deposition technique. The films were characterized using an x-ray diffraction, atomic force microscopy, and infrared reflectance spectroscopy. The films grown on STO (001) substrate show a compressive in-plane strain which increases as the film thickness is reduced resulting in an increase of the NiO phonon frequency. On the other hand, a tensile strain was detected in the NiO film gr
MnO thin films with various thicknesses and strains were grown on MgO substrates by pulsed laser deposition technique, then characterized using x-ray diffraction and infrared reflectance spectroscopy. Films grown on (0 0 1)-oriented MgO substrates exhibit homogenous biaxial compressive strain which increases as the film thickness is reduced. For that reason, in paramagnetic phase, the frequency of doubly-degenerate phonon increases with the strain, and splits below Néel temperature T <sub>N</sub
Abstract The reliability of hafnia‐based ferroelectrics at operating voltages below 1 V, the required voltage range for compatibility with advanced nodes, remains unexplored. Additionally, the impact of the position and conductivity of the interfacial layer (IL) on capacitor characteristics is not well understood. In this study, an Hf 1‐X Zr X O 2 capacitor capable of ultra‐low operation voltage (<1 V) is developed with excellent endurance (>10 11 cycles) and retention (>10 years at 85
In the era of artificial intelligence, the demand for performance has lent a powerful impetus to researchers and scientists to expand the horizons of semiconductor memory devices. Among the emerging nonvolatile memories, ferroelectric random-access memory (FeRAM) is one of the best resources for all kinds of applications. FeRAMs utilize the two stored switchable polarization states of ferroelectric materials as binary codes. This class of memory was introduced in the 1980s and is based on perovs
Wake-up effect is still an obstacle in the commercialization of hafnia-based ferroelectric thin films. In this work, we investigate the effect of defects, controlled by ozone dosage, on the field cycling behavior of the atomic layer deposited Hf0.5Zr0.5O2 (HZO) films. A nearly wake-up free device was achieved after reduction of carbon contamination and oxygen defects by increasing the ozone dosage. The sample which was grown at 30 sec ozone pulse duration shows about 98% of the woken-up Pr at th
