Browsing by Subject "Si nanoparticles"

Now showing 1 - 4 of 4

Open Access
2-nm laser-synthesized Si nanoparticles for low-power charge trapping memory devices
(IEEE, 2014-08) El-Atab, N.; Özcan, Ayşe; Alkış, Sabri; Okyay, Ali Kemal; Nayfeh, A.
In this work, the effect of embedding Silicon Nanoparticles (Si-NPs) in ZnO based charge trapping memory devices is studied. Si-NPs are fabricated by laser ablation of a silicon wafer in deionized water followed by sonication and filtration. The active layer of the memory was deposited by Atomic Layer Deposition (ALD) and spin coating technique was used to deliver the Si-NPs across the sample. The nanoparticles provided a good retention of charges (>10 years) in the memory cells and allowed for a large threshold voltage (Vt) shift (3.4 V) at reduced programming voltages (1 V). The addition of ZnO to the charge trapping media enhanced the electric field across the tunnel oxide and allowed for larger memory window at lower operating voltages. © 2014 IEEE.
Open Access
Low power Zinc-Oxide based charge trapping memory with embedded silicon nanoparticles
(ECS, 2014) Nayfeh, A.; Okyay, Ali Kemal; El-Atab, N.; Özcan, Ayşe; Alkış, Sabri
In this work, a bottom-gate charge trapping memory device with Zinc-Oxide (ZnO) channel and 2-nm Si nanoparticles (Si-NPs) embedded in ZnO charge trapping layer is demonstrated. The active layers of the memory device are deposited by atomic layer deposition (ALD) and the Si-NPs are deposited by spin coating. The Si-NPs memory exhibits a threshold voltage (Vt) shift of 6.3 V at an operating voltage of -10/10 V while 2.6 V Vt shift is obtained without nanoparticles confirming that the Si-NPs act as energy states within the bandgap of the ZnO layer. In addition, a 3.4 V Vt is achieved at a very low operating voltage of -1 V/1 V due to the charging of the Si-NPs through Poole-Frenkel emission mechanism at an electric field across the tunnel oxide E > 0.36 MV/cm. The results highlight a promising technology for future ultra-low power memory devices.
Open Access
Post-Treatment od Silicon Nanocrystals Produced by Ultra-Short Pulsed Laser Ablation in Liquid: Toward Blue Luminescent Nanocrystal Generation
(American Chemical Society, 2012-01-11) Alkis, S.; Okyay, Ali Kemal; Ortac, B.
Blue luminescent colloidal silicon nanocrystals (Si-NCs) were produced in a two-stage process. In the first step, synthesis of Si-NCs was achieved by femtosecond pulsed laser ablation of a silicon wafer, which was immersed in deionized water. The size and the structural and the chemical characteristics of colloidal Si-NCs were investigated by TEM and EDAX analyses, and it is found out that the Si-NCs are in spherical shape and the particle diameters are in the range of 5-100 nm. In the second step, ultrasonic waves and filtering chemical-free post-treatment of colloidal Si-NCs solution was performed to reduce the particle size. High-resolution TEM (HRTEM) studies on post-treated colloidal solution clearly show that small (1-5.5 nm in diameter) Si-NCs were successfully produced. Raman spectroscopy results clearly confirms the generation of Si nanoparticles in the crystalline nature, and the Raman scattering study of post-treated Si-NCs confirms the reduction of the particle size. The UV-vis absorption and photoluminescence (PL) spectroscopy studies elucidate the quantum confinement effect of Si-NCs on the optical properties. The colloidal Si-NCs and post-treated Si-NCs solutions present strong absorption edge shifts toward UV region. Broadband PL emission behavior is observed for the initial colloidal Si-NCs, and the PL spectrum of post-treated Si-NCs presents a blue-shifted broadband PL emission behavior due to the particle size reduction effect.
Open Access
Silicon nanoparticle charge trapping memory cell
(Wiley-VCH Verlag, 2014) El-Atab, N.; Ozcan, A.; Alkis, S.; Okyay, Ali Kemal; Nayfeh, A.
A charge trapping memory with 2 nm silicon nanoparticles (Si NPs) is demonstrated. A zinc oxide (ZnO) active layer is deposited by atomic layer deposition (ALD), preceded by Al2O3 which acts as the gate, blocking and tunneling oxide. Spin coating technique is used to deposit Si NPs across the sample between Al2O3 steps. The Si nanoparticle memory exhibits a threshold voltage (Vt) shift of 2.9 V at a negative programming voltage of -10 V indicating that holes are emitted from channel to charge trapping layer. The negligible measured Vt shift without the nanoparticles and the good re- tention of charges (>10 years) with Si NPs confirm that the Si NPs act as deep energy states within the bandgap of the Al2O3 layer. In order to determine the mechanism for hole emission, we study the effect of the electric field across the tunnel oxide on the magnitude and trend of the Vt shift. The Vt shift is only achieved at electric fields above 1 MV/cm. This high field indicates that tunneling is the main mechanism. More specifically, phonon-assisted tunneling (PAT) dominates at electric fields between 1.2 MV/cm < E < 2.1 MV/cm, while Fowler-Nordheim tunneling leads at higher fields (E > 2.1 MV/cm). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.