Browsing by Subject "Charge trapping layers"

Now showing 1 - 6 of 6

Open Access
Charge Trapping Memory with 2.85-nm Si-Nanoparticles Embedded in HfO2
(ECS, 2015-05) El-Atab, N.; Turgut, Berk Berkan; Okyay, Ali Kemal; Nayfeh, A.
In this work, the effect of embedding 2.85-nm Si-nanoparticles charge trapping layer in between double layers of high-κ Al2O3/HfO2 oxides is studied. Using high frequency (1 MHz) C-Vgate measurements, the memory showed a large memory window at low program/erase voltages due to the charging of the Si-nanoparticles. The analysis of the C-V characteristics shows that mixed charges are being stored in the Si-nanoparticles where electrons get stored during the program operation while holes dominate in the Si-nanoparticles during the erase operation. Moreover, the retention characteristic of the memory is studied by measuring the memory hysteresis in time. The obtained retention characteristic (35.5% charge loss in 10 years) is due to the large conduction and valence band offsets between the Si-nanoparticles and the Al2O3/HfO2 tunnel oxide. The results show that band engineering is essential in future low-power non-volatile memory devices. In addition, the results show that Si-nanoparticles are promising in memory applications.
Open Access
Cubic-phase zirconia nano-island growth using atomic layer deposition and application in low-power charge-trapping nonvolatile-memory devices
(Institute of Physics Publishing Ltd., 2017) El-Atab, N.; Ulusoy, T. G.; Ghobadi, A.; Suh, J.; Islam, R.; Okyay, Ali Kemal; Saraswat, K.; Nayfeh, A.
The manipulation of matter at the nanoscale enables the generation of properties in a material that would otherwise be challenging or impossible to realize in the bulk state. Here, we demonstrate growth of zirconia nano-islands using atomic layer deposition on different substrate terminations. Transmission electron microscopy and Raman measurements indicate that the nano-islands consist of nano-crystallites of the cubic-crystalline phase, which results in a higher dielectric constant (κ ∼ 35) than the amorphous phase case (κ ∼ 20). X-ray photoelectron spectroscopy measurements show that a deep quantum well is formed in the Al2O3/ZrO2/Al2O3 system, which is substantially different to that in the bulk state of zirconia and is more favorable for memory application. Finally, a memory device with a ZrO2 nano-island charge-trapping layer is fabricated, and a wide memory window of 4.5 V is obtained at a low programming voltage of 5 V due to the large dielectric constant of the islands in addition to excellent endurance and retention characteristics.
Open Access
Graphene Nanoplatelets Embedded in HfO2 for MOS Memory
(Electrochemical Society Inc., 2015) El-Atab, N.; Turgut, Berk Berkan; Okyay, Ali Kemal; Nayfeh, A.
In this work, a MOS memory with graphene nanoplatelets charge trapping layer and a double layer high-κ Al2O3/HfO2 tunnel oxide is demonstrated. Using C-Vgate measurements, the memory showed a large memory window at low program/erase voltages. The analysis of the C-V characteristics shows that electrons are being stored in the graphene-nanoplatelets during the program operation. In addition, the retention characteristic of the memory is studied by plotting the hysteresis measurement vs. time. The measured excellent retention characteristic (28.8% charge loss in 10 years) is due to the large electron affinity of the graphene. The analysis of the plot of the energy band diagram of the MOS structure further proves its good retention characteristic. Finally, the results show that such graphene nanoplatelets are promising in future low-power non-volatile memory devices.
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
Low power zinc-oxide based charge trapping memory with embedded silicon nanoparticles via poole-frenkel hole emission
(2014) El-Atab, N.; Ozcan, A.; Alkis, S.; Okyay, Ali Kemal; Nayfeh, A.
A low power zinc-oxide (ZnO) charge trapping memory with embedded silicon (Si) nanoparticles is demonstrated. The charge trapping layer is formed by spin coating 2 nm silicon nanoparticles between Atomic Layer Deposited ZnO steps. The threshold voltage shift (ΔVt) vs. programming voltage is studied with and without the silicon nanoparticles. Applying -1 V for 5 s at the gate of the memory with nanoparticles results in a ΔVt of 3.4 V, and the memory window can be up to 8 V with an excellent retention characteristic (>10 yr). Without nanoparticles, at -1 V programming voltage, the ΔVt is negligible. In order to get ΔVt of 3.4 V without nanoparticles, programming voltage in excess of 10 V is required. The negative voltage on the gate programs the memory indicating that holes are being trapped in the charge trapping layer. In addition, at 1 V the electric field across the 3.6 nm tunnel oxide is calculated to be 0.36 MV/cm, which is too small for significant tunneling. Moreover, the ΔVt vs. electric field across the tunnel oxide shows square root dependence at low fields (E 1 MV/cm) and a square dependence at higher fields (E > 2.7 MV/cm). This indicates that Poole-Frenkel Effect is the main mechanism for holes emission at low fields and Phonon Assisted Tunneling at higher fields. © 2014 AIP Publishing LLC.
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.