Resistance switching is studied in conductive bridge memory structures made from atomic layer deposited HfO
2
and Ag active electrode. Inert electrode is varied by using different substrates (TiN, W, ...Pt). HfO
2
crystallinity is modified by varying the deposition temperature (300/350 °C) and the film thickness (10/20 nm). Current–voltage characteristics, as well as current–time characteristics (to access to the switching kinetics), are studied according to the inert electrode nature and HfO
2
structural properties. Results are discussed along resistance transition mechanisms which imply (i) the generation of oxygen vacancies by electronic injection at the inert electrode, (ii) Ag diffusion along oxygen vacancy paths, and (iii) the reduction of silver ions controlled by the inert electrode/HfO
2
interface. Best characteristics, in terms of stability, are observed with Pt inert electrode and 10 nm films. Crystalline and amorphous films (10 nm) provide similar characteristics. In 10 nm films, TiN and W inert electrodes lead to variability in electrical properties (parasitic sets during reset, switching time dispersion). Such a variability is related to high electronic injection at the TiN/HfO
2
and W/HfO
2
interfaces which creates a high density of oxygen vacancy paths (Ag diffusion paths). In thicker and well-crystallized films (20 nm), progressive set is observed. This is ascribed to conduction along oxygen vacancy paths, which dominates over conduction along Ag conductive bridges.
In this work, we study the impact of roughness of TiN bottom electrode on the forming voltage of 1R TiN/HfO2/Ti/TiN based ReRAM devices. A novel and atypical strategy is proposed to induce a ...controlled roughness of the bottom electrode, using various plasma chemistries. The forming voltage is observed to be directly linked to the roughness of the bottom electrode, over a large range of roughness values. TCAD simulation studies enable an estimate of the electrical field in the oxide inducing the forming step and confirm the dominant impact of roughness on the switching properties of ReRAM devices.
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•Evolution of the forming voltage of HfO2-based resistive memories as function of the roughness of TiN Bottom Electrode.•Large range of roughness values of TiN Bottom Electrode achieved.•Whatever plasma chemistry used, the forming voltage decreases when mean (or maximum) roughness values increase.•Saturation of the forming voltage for mean roughness values of 3 nm.•Saturation of the forming voltage consistent with TCAD simulations.
In this paper, memory devices integrating a double layer of silicon nanocrystals (Si-ncs) as a trapping medium and a HfAlO-based control dielectrics are presented. We will show that the use of two ...stacked Si-nc layers significantly improves the memory window compared with the single Si-nc layer devices, without introducing anomalies on the charging dynamics. Then, we also evaluate the potential use of a hybrid Si-nc double-layer/SiN layer charge trapping stack. These devices show a good memory window in a Fowler-Nordheim (FN)/FN mode and a good retention (>; 3 V after ten years) with small activation energy (0.35 eV up to 200 °C), thus showing promise for future high-temperature memory applications. A model implying valence-band electron tunneling and a floating-gate-like approximation is used to explain the memory window improvement of the Si-nc double-layer memory devices.
The Smart-Cutregistered trademark process, based on ion implantation (hydrogen, helium) and wafer bonding, appears more and more as a generic process. The first part of the paper is dedicated to the ...specific case of thermally-induced splitting. Cavity growth by the Ostwald ripening mechanism and crack propagation are responsible for thermally-induced splitting. In this case, the splitting kinetics are controlled by hydrogen diffusion. In the second part, the latest results concerning new structures are presented.
III-V layer transfer onto silicon and applications Di Cioccio, L.; Jalaguier, E.; Letertre, F.
Physica status solidi. A, Applications and materials science,
March 2005, Volume:
202, Issue:
4
Journal Article
In this paper, a physical investigation of hybrid molecular/Si memory capacitor structures is proposed, where redox-active molecules act as storage medium. Fc and ZnAB 3 P porphyrin were grafted on ...(100) Si with both a direct bond and a chemical linker in order to investigate the electron transfer properties of the molecule/Si system. The chemical structures of the molecular layers were analyzed with X-ray photoelectron spectroscopy. Cyclic voltammetry and impedance spectroscopy were also performed on capacitor structures in order to characterize the charge transfer between the redox molecules and the Si and the effect of an organic linker on its rate. To explain our results, an original electrical model of molecule/Si memory structures is proposed. Calculated data are compared to impedance results for the cases of Fc either directly grafted or with linker. The model allows us to give a theoretical confirmation of the influence of the linker over the redox energy and on the time constant of the molecular capacitor. Finally, density functional theory calculations provide an in-depth physical insight of the effect of the linker over the Fc redox energy. The results obtained in this paper show the strong impact of the engineering of the redox molecules and their linker on the electron transfer properties.
We show experimentally that the first reset operation of forming-free HfOx based RRAM devices is of bulk type where the reset current is area dependent. Moreover, the device pristine resistance shows ...a weak inverse proportionality to temperature, which we associate to a sub-stoichiometric HfOx matrix created during device fabrication. Finally, we use ab initio calculations to gain insight into the atomistic structure of these forming-free RRAM devices.
In this work, we study the impact of roughness of TiN bottom electrode on the forming voltage of 1R TiN/HfO$_2$/Ti/TiN based ReRAM devices. A novel and atypical strategy is proposed to induce a ...controlled roughness of the bottom electrode, using various plasma chemistries. The forming voltage is observed to be directly linked to the roughness of the bottom electrode, over a large range of roughness values. TCAD simulation studies enable an estimate of the electrical field in the oxide inducing the forming step and confirm the dominant impact of roughness on the switching properties of ReRAM devices.
We report results on hexagonal-shaped microlasers formed from two-dimensional photonic crystals (PCs) using InP-based materials transferred and bonded onto SiO/sub 2// Si wafers. Two types of ...hexagonal cavities are investigated : single defect (one hole missing) cavities, so-called H1 cavities (1 /spl mu/m in diameter) and two holes missing per side H2 cavities (2 /spl mu/m in diameter). Their optical properties are analyzed using photoluminescence experiments, and plane wave method simulations have been performed for comparison. High Q modes (/spl sim/600/700) have been measured and they have been shown to enable laser effect at room temperature, under pulsed optical pumping (15% duty cycle and 25-ns pulsewidth). The study of these efficient mode characteristics gives guidance for further improvement of the operation conditions of PC lasers, such as the reduction of the threshold pumping power.
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