Faiz Dahmani

Sb-doped GeS 2 as performance and reliability booster in Conductive Bridge RAM

In this work, for the first time at our knowledge, the improvement of chalcogenide-based CBRAM performance and reliability by Sb doping of the GeS2 electrolyte is presented. An original analysis, based on in-depth physico-chemical characterization, device electrical measurements, empirical model and first principle calculations, is shown. We argue that optimized ~10% Sb doping in the GeS2 electrolyte allows to achieve SET speed of 30ns at 2.2V (i.e. 0.66pJ SET programming power), while assuring 10 years data retention at 125°C, >105 cycling and high robustness to Sn-Pb soldering profile. Finally, the improved thermal stability of the filament in the GeS2-Sb matrix is clearly elucidated by means of molecular dynamics calculations.

Controlling oxygen vacancies in doped oxide based CBRAM for improved memory performances

In this paper the concept hybrid CBRAM assisted by oxygen vacancies is presented for the 1<;sup>st<;/sup> time. Doping the resistive layer of oxide/Cu based CBRAM with <; dopant species and concentrations is proposed in order to improve the memory performances. By means of experimental characterizations, numerical model and atomistic calculations, we demonstrate that increasing the doping content ease the filament formation by facilitating the Cu injection in the resistive layer. The proper choice of the doping element and concentration allows to significantly reduce the forming voltage (up to a forming free behavior), or alternatively to increase the memory window of 3 decades, with no forming voltage increase and retention degradation (stable behavior at 200°C, 260°C soldering sustained).

Experimental scaling laws for mass‐ablation rate, ablation pressure in planar laser‐produced plasmas with laser intensity, laser wavelength, and target atomic number

Layered‐target experiments at 1.06 μm for carbon and silicon materials have been carried out to measure mass‐ablation rate m and ablation pressure Pa as a function of absorbed laser intensity Ia, laser wavelength λL, and target atomic number Z at irradiances of 1013–1015 W/cm2. The results can be put in the forms m(kg/s cm2)≂55 [Ia(W/cm2)/1014]1/3λL−4/3(μm) Z3/8 and Pa(Mbar)≂7.4 [Ia(W/cm2)/1014]2/3λL−2/3(μm) Z3/16. The experimental data are compared with one‐dimensional hydrodynamic calculations (code medusa) using different values of electron heat‐flux limitation. An indication of laser intensity, target atomic number dependent on flux inhibition was found: 0.06≤f≤0.08 for silicon targets and f=0.015–0.03 for carbon targets. These flux limitations are discussed in terms of a small lateral transport and an eventual presence of intense magnetic fields.

Effect of the Active Layer Thickness and Temperature on the Switching Kinetics of GeS2-Based Conductive Bridge Memories

In this paper, the effect of the active layer thickness and temperature on the switching kinetics of GeS2-based conductive bridge memories is addressed through electrical characterization. Results are explained in terms of a thermally and field driven ion hopping model for reversible resistance switching. The combined analysis reveals that at high temperature the set voltage and the set resistance decrease. Furthermore, the study suggests that applying the same reset condition, for GeS2 thicknesses lower than 50 nm, the conductive filament is almost dissolved, while for thicker layers a portion of the filament still remains.

Experimental Investigation and Empirical Modeling of the Set and Reset Kinetics of Ag-GeS2 Conductive Bridging Memories

In this paper, we present a new empirical model able to explain the main features of set and reset processes in Ag-GeS2 Conductive Bridging Memories. The model is carefully validated on a wide number of experimental data, precisely designed for this scope. In particular, electrical tests were performed both in quasi static and in pulse modes on industrial CBRAM cells. The simulations here reported provide new insights on the device operations as well as clear indications for the development of CBRAM compact-modeling suitable for design implementation.

On the impact of Ag doping on performance and reliability of GeS 2 -based Conductive Bridge Memories

In this work, we study the impact of Ag doping on GeS2-based CBRAM devices employing Ag as active electrode. Several devices with Ag doping varying between 10% and 24% are extensively analyzed. First, we assess switching voltages and time-to-set as a function of Ag concentration in the electrolyte layer. Subsequently, we evaluate data retention at different temperatures. The results show that a Ag doping increase in the GeS2 yields a strong improvement on data retention performance, increasing the 10-years data-ret temperature from 68°C for the 10% Ag doping to 100°C for the 24%, without any significant increase of the set voltage (50mV higher).

Influence of reference layer stability on the switching performance of sub-micron-sized magnetic tunnel junctions

Arrays of sub-micron-sized, magnetic tunnel junctions are patterned and the switching field (Hc) of the free layer (FL) and its distribution (σ) are measured by Kerr magnetometry. A correlation of Hc and σ with the magnetic stiffness (stability against external magnetic fields) of the reference system (RS) is observed. For simple pinned RSs the stiffness is varied by different materials (CoFe vs CoFeB) and its thicknesses, while for artificial antiferromagnetic pinned systems the thickness of the exchange coupling layer of Ruthenium is modified. It is shown that less stiffness causes a lower Hc and larger σ. This effect is assumed to be due to magnetic mirror charges induced in RS by the magnetic dipoles of the patterned FL elements. These mirror charges screen the dipole stray field of the FL resulting in lower effective shape anisotropy, which goes along with reduced switching fields. Micromagnetic simulations performed for different pinning strengths of a single layer RS clearly support this observatio...

Effect of Seed Layer on Room Temperature Tunnel Magnetoresistance of MgO Barriers Formed by Radical Oxidation in IrMn-Based Magnetic Tunnel Junctions

NiFe-seeded magnetic tunnel junctions (MTJs) of IrMn/CoFe/MgO/CoFeB were successfully formed by radically oxidizing a thin Mg layer. Room temperature (RT) tunnel magnetoresistance (TMR) of up to 211±10% was obtained and found to be strongly dependent on the thickness of the NiFe seed layer. High resolution transmission microscopy (HRTEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and magneto-optic Kerr effect (MOKE) analyses performed on NiFe/IrMn bilayer systems revealed that the IrMn(111)-fcc texture, grain size, surface roughness (rms), and exchange-biasing field (Hex) were strongly affected by the thickness of the NiFe seed layer. A critical NiFe thickness (tc ≈12 A) was found: For tNiFe≤tc, the IrMn showed a very poor (111)-fcc texture with reduced grain size, very smooth surface, and reduced Hex. For tNiFe > tc, the IrMn showed a complete opposite behavior: much enhanced (111)-fcc texture with larger grain size, rougher surface, and larger Hex. For MTJ-based IrMn systems, a striking behavior is reported: larger TMRs and lower tunnel junction resistance (RA) products are obtained for tNiFe ≤tc while lower TMRs and larger RAs are obtained for tNiFe > tc.