BILKENT UNIVERSITY
DEPARTMENT of PHYSICS SEMINAR
Prof. Dr. M. Alper Şahiner
Seton Hall University
*Currently Fulbright Distinguished Scholar at Gebze Technical University
“Ferroelectricity in HfO2 -based Thin Films: A Local Structural Approach”
Abstract:
HfO2 -based ferroelectrics have become important for future applications in CMOS technology such as negative capacitance low-power field effect transistor (FET) logic, FeRAM or FeFET memory, and FeFET- or ferroelectric tunnel junction (FTJ)-based neural network accelerators. I will describe a synchrotron radiation based local structural X-ray spectroscopy probe to identify the crystalline phases present in HfO2 based thin films used in semiconductor industry. In our previous studies, we have used density-functional theory (DFT)-assisted extended X-ray absorption fine-structure spectroscopy (EXAFS) to identify the crystalline phases in the films of (Hf0.46Zr0.54O2 ) as grown by atomic layer deposition [1]. In these films, Ferroelectric switching in TiN/Hf0.46Zr0.54O2 /TiN metal-insulator-metal capacitors is verified. We confirmed that the frequently invoked polar orthorhombic Pca21 phase is present in ferroelectric hafnium zirconium oxide, along with an equal amount of the non-polar monoclinic P21 /c phase. For comparison, we verified that paraelectric HfO2 films exhibit the P21 /c phase. In this study we are extending our studies to identify the crystalline phases in Al-doped HfO2 thin films. We have again used density functional theory (DFT)-assisted extended X-ray absorption fine-structure spectroscopy (EXAFS) to determine the structural symmetry of Al doped HfO2 thin films. The 8-nm thick HfO2-based films were grown by atomic layer deposition in a metal-insulator-metal (MIM) stack configuration with varying doping levels Al and annealing temperatures. Grazing-incidence fluorescence-yield mode Hf L3 and Zr K absorption edge EXAFS experiments were performed at the 6-BM beamline at the National Synchrotron Light Source II of Brookhaven National Laboratory. The results of the EXAFS multiphase fitting and the effect of Al doping levels to crystalline phases will be discussed in conjunction with the electrical properties.
Dr. M. Alper Şahiner received his BS in EE and BS in Physics degrees (double major) from Bogazici University in 1989. He completed his Ph.D. in Physics at Rutgers University in 1995. After finishing his post-doctoral studies at Simon Fraser University, he worked at the Brookhaven National Laboratory as a scientist in the period of 1997-1999. During 1999-2003 he worked as a senior scientist at Evans Analytical Group, which is the distinguished worldwide network of materials characterization laboratories worldwide. After joining Seton Hall University, New Jersey in 2003, Dr. Sahiner founded the Advanced Materials Synthesis and Characterization Laboratory (AMSCL). His research interests are in semiconductor materials. He is looking for solutions for the major materials-based problems of the semiconductor industry by developing novel materials. His recent research also focuses on developing thin film based high-efficiency solar cells with conducting polymer capping and metal nanoparticle inclusions. His research has been supported by grants from National Science Foundation, Department of Energy, Department of Defense, SEMATECH, and Cottrell Research Foundation, CSIC-Madrid. He was inducted to Sigma Pi Sigma Physics Honor Society in 2012. He was promoted to Associate Professor in 2008 and full professor in 2013 and has been serving as the Chair of the Department of Physics at Seton Hall University since 2009. He is also serving on the Editorial Board of Materials Science in Semiconductor Processing (Elsevier). He has authored over 50 scientific publications, 134 presentations (32 plenary or invited talks), a book chapter, and brought Seton Hall University over $1,500,000 extramural funding to SHU during his tenure. Most recently, he has been collaborating with researchers at IBM T.J. Watson Research Center and NIST, and Brookhaven National Laboratory on newly discovered Hafnium based ferroelectric memory devices for the next generation of computers. He is currently at the Gebze Technical University as a Fulbright Distinguished Professor.
Date: March 20, 2024 Wednesday
Time: 15:30
Place: SA-240
All interested are cordially invited.