The effect of stress-triaxiality on growth of a void in a three dimensional single-crystal facecentered-cubic (FCC) lattice has been studied. Molecular dynamics (MD) simulations using an embedded-atom (EAM) potential for copper have been performed at room temperature and using strain controlling with high strain rates ranging from 10 7 /sec to 10 10 /sec. Strain-rates of these magnitudes can be studied experimentally, e.g. using shock waves induced by laser ablation. Void growth has been simulated in three different conditions, namely uniaxial, biaxial, and triaxial expansion. The response of the system in the three cases have been compared in terms of the void growth rate, the detailed void shape evolution, and the stress-strain behavior including the development of plastic strain. Also macroscopic observables as plastic work and porosity have been computed from the atomistic level. The stress thresholds for void growth are found to be comparable with spall strength values determined by dynamic fracture experiments. The conventional macroscopic assumption that the mean plastic strain results from the growth of the void is validated. The evolution of the system in the uniaxial case is found to exhibit four different regimes: elastic expansion; plastic yielding, when the mean stress is nearly constant, but the stress-triaxiality increases rapidly together with exponential growth of the void; saturation of the stress-triaxiality; and finally the failure.

We analyze intermittence and roughening of an elastic interface or domain wall pinned in a periodic potential, in the presence of random-bond disorder in 1+1 and 2+1 dimensions. Though the ensemble average behavior is smooth, the typical behavior of a large sample is intermittent, and does not self-average to a smooth behavior. Instead, large fluctuations occur in the mean location of the interface and the onset of interface roughening is via an extensive fluctuation which leads to a jump in the roughness of order lambda, the period of the potential. Analytical arguments based on extreme statistics are given for the number of the minima of the periodicity visited by the interface and for the roughening crossover, which is confirmed by extensive exact ground state calculations.

Monodisperse nanoparticles of well-defined size and shape are required in several emerging applications, which take advantage of their size-dependent properties such as the superparamagnetic limit in the case of magnetic nanoparticles. [1,2] Accurate tuning of the nanoparticle size and shape requires understanding of the mechanisms involved in particle nucleation and growth. [3][4][5] In spite of extensive ongoing research, these mechanisms are still not fully understood owing to their complexity and interplay. Moreover, the current small-scale synthesis methods, such as the hotinjection method, can be difficult to scale to industrially relevant levels. Hence, more suitable methods are sought. [6][7][8][9][10][11][12][13][14][15][16][17][18][19] Herein, we revisit a widely studied hot-injection synthesis of monodisperse cobalt nanoparticles [20][21][22][23][24][25][26] and show that the particle nucleation differs from what is expected for a hotinjection synthesis. Evidence is given that the particles nucleate several tens of seconds or a few minutes after the injection, depending delicately on how the reaction temperature is controlled after the sudden temperature drop caused by the injection. The delayed nucleation is followed by a period during which the cobalt precursor decomposes endothermically, the temperature drops, carbon monoxide evolves, and the nuclei rapidly grow into mature nanoparticles. Particle growth after the endothermic period is negligible, and we show that the final particle size is determined by the rate of temperature increase after the injection-induced temperature drop. A rapid increase results in a higher peak temperature before the endothermic period and more nuclei, hence smaller particles, in comparison to the case of a slower rate of temperature increase. The contribution of the injection to particle nucleation seems minor, and it is shown that injection can be replaced entirely by an accurately controlled heating up of the solution containing all reagents (including the cobalt precursor) from room temperature to the nucleation temperature. This synthetic method, which is often termed either "non-injection synthesis" [15,16] or "heating-up synthesis", [3,11] results in nanoparticles that are nearly identical to those made by the hot-injection method.We synthesized cobalt nanoparticles by injecting dicobalt octacarbonyl, [Co 2 (CO) 8 ], dissolved in a small amount of ortho-dichlorobenzene (o-DCB, b.p. 181 8C) into a solution of oleic acid and trioctylphosphine oxide (TOPO) in o-DCB at reflux.[20] The injection led to an immediate temperature drop of several tens of degrees, which is characteristic of the hotinjection method in general.[ [25,27] It has been shown that both maintaining the lower temperature and letting the temperature recover to the reflux temperature after the injection can lead to monodisperse nanoparticles. [20][21][22][23] In this study, we concentrated on the latter approach and studied for the first time in detail the kinetics of the temperature recovery to refl...

We report for the first time the demonstration of 3D integrated circuits obtained by die-to-die stacking using Cu Through Silicon Vias (TSV). The Cu TSV process is inserted between contact and M1 of our reference 0.13µm CMOS process on 200mm wafers. The top die is thinned down to 25µm and bonded to the landing wafer by Cu-Cu thermo-compression. Both top and landing wafers contain CMOS finished at M2 to evaluate the process impact both FEOL and BEOL. The results confirm no degradation of the FEOL performance. The functionality of various ring oscillator topologies that include inverters distributed over both top and bottom dies connected through TSVs demonstrates excellent chip integrity after the TSV and 3D stacking process. 3D-SIC processRecently 3D integration has gained a lot of interest due to its potential to alleviate some important performance limitations facing CMOS scaling and because it enables so-called heterogeneous integration [1][2]. Different approaches to 3D integration are reported depending on system level requirements [3]. Our 3D Stacked IC (3D-SIC) process [4][5] uses IC foundry infrastructure to create Through Silicon Vias (TSVs) prior to BEOL processing. The main advantage of this approach is the fact that it has minimal impact on both FEOL and BEOL design and processing. Furthermore it offers very high TSV densities. The TSV process sequence is summarized in Fig. 1. Figure 1: Schematic of the 3D-SIC Through Silicon Via (TSV) module.After processing of the CMOS FEOL and the PMD stack, we patterned TSVs with a diameter of 5µm and a pitch of 10µm using a 3µm thick I-line resist. We performed an undercut free, resist-based TSV etch (Fig. 2); undercut underneath the contact layer is avoided by pre-deposition of a polymer on the sidewall of the etched PMD/STI stack prior to the Si etch. For electrical isolation, we deposit a 100nm SACVD O 3 -TEOS layer. The metallization sequence consists of applying a 80nm PVD Ta barrier and a 300nm PVD Cu seed followed by an ECD via fill using a 3-component plating chemistry. Finally the Cu overburden is polished in a top-side TSV CMP step (Fig. 3). After this process, we apply a standard, 2 metal layer BEOL process to finalize the top Si-die. Figure 2&3: FIB through TSV in vicinity of device after etch, strip& clean (left), and after TSV CMP and sintering (right). (Pt on top for contrast).After wafer test, the wafer is mounted on a temporary carrier and thinned down to a Si-thickness of ~25 m by a combination of grinding and CMP. In this process, the TSVs are exposed on the wafer backside. Next the Si is recessed by dry etching over a distance of ~700nm with respect to the copper TSV. In this work the dies were then stacked by Cu-Cu thermo-compression bonding in a Die-to-Die (D2D) fashion, although compatibility with Die-to-Wafer integration remains. Figure 4 shows an optical 3D reconstruction of the obtained 3D stack. Figure 4: Optical 3D reconstruction based on multiple images at different height of thinned top die stacked to a bottom die by Cu-Cu bonding.

Ground states and domain walls are investigated with exact combinatorial optimization in two-dimensional random field Ising magnets. The ground states break into domains above a length scale that depends exponentially on the random field strength squared. For weak disorder, this paramagnetic structure has remnant longrange order of the percolation type. The domain walls are super-rough in ordered systems with a roughness exponent close to 6/5. The interfaces exhibit rare fluctuations and multiscaling reminiscent of some models of kinetic roughening and hydrodynamic turbulence.