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Herein, a low RESET current 1T1R mushroom‐cell phase‐change memory (PCM) device that uses fiber‐textured homostructure GeSbTe (GST) grown on highly oriented TiTe2 seed layer is reported. The homostructure device outperformed the industry standard device, that uses doped polycrystalline GST, on most figures of merit. The homostructure devices are also benchmarked against superlattice (SL) PCM devices with 10 periods of 5/5 nm GST/Sb2Te3 grown on the TiTe2 seed layer, and are found to have same low RESET current. It is also observed by transmission electron microscopy that the alternating layers of GST/Sb2Te3 and TiTe2/Sb2Te3 in SL devices are intermixed in the switched region after the devices are cycled with RESET/SET pulses. Additionally, when the SL device is left in the SET state, the intermixed switched region crystallinity is textured and exhibits van der Waals gaps. The SL PCM devices require a precise layered structure that is hard to yield on a full wafer scale. In contrast, fiber‐textured homostructure PCM cells reported here are easily manufacturable, while providing similarly low RESET current and low‐resistance drift, which makes this device suitable for analog artificial intelligence computation. [ABSTRACT FROM AUTHOR]

Material properties of Ga–Sb binary alloy thin films deposited under ultra-high vacuum conditions were studied for analog phase change memory (PCM) applications. Crystallization of this alloy was shown to occur in the temperature range of 180–264 °C, with activation energy >2.5 eV depending on the composition. X-ray diffraction (XRD) studies showed phase separation upon crystallization into two phases, Ga-doped A7 antimony and cubic zinc-blende GaSb. Synchrotron in situ XRD analysis revealed that crystallization into the A7 phase is accompanied by Ga out-diffusion from the grains. X-ray absorption fine structure studies of the local structure of these alloys demonstrated a bond length decrease with a stable coordination number of 4 upon amorphous-to-crystalline phase transformation. Mushroom cell structures built with Ga–Sb alloys on ø110 nm TiN heater show a phase change material resistance switching behavior with resistance ratio >100 under electrical pulse measurements. TEM and Energy Dispersive Spectroscopy (EDS) studies of the Ga–Sb cells after ∼100 switching cycles revealed that partial SET or intermediate resistance states are attained by the variation of the grain size of the material as well as the Ga content in the A7 phase. A mechanism for a reversible composition control is proposed for analog cell performance. These results indicate that Te-free Ga–Sb binary alloys are potential candidates for analog PCM applications. [ABSTRACT FROM AUTHOR]

This work describes an ab initio study of the electronic structure, electron transport, and energetic properties of cobalt disilicide (CoSi2) and nickel disilicide (NiSi2) nanowires with widths ranging from approximately 0.5 to 2.5 nm using density functional theory. The effects of oxidation on the nanowire surface are considered and are found to reduce the ballistic conductance by approximately 27% for both species considered. The cohesive energies for both the bulk species as well as the nanowires are found to be significantly stronger than for copper, indicating excellent structural stability. While the lower limit of electrical resistance calculated via the ballistic conductance is still significantly larger than that of Cu nanowires of comparable dimensions, the strong intrinsic lattice energy of the disilicide nanowires suggests that they can be fabricated without the need for diffusion barriers and will exhibit superior resistance to self-diffusion and electromigration. [ABSTRACT FROM AUTHOR]

We report the formation of very uniform and smooth Ni(Pt)Si on epitaxially grown SiGe using Si gas cluster ion beam treatment after metal-rich silicide formation. The gas cluster ion implantation process was optimized to infuse Si into the metal-rich silicide layer and lowered the NiSi nucleation temperature significantly according to in situ X-ray diffraction measurements. This novel method which leads to more uniform films can also be used to control silicide depth in ultrashallow junctions, especially for high Ge containing devices, where silicidation is problematic as it leads to much rougher interfaces. [ABSTRACT FROM AUTHOR]

A multi-technique approach was used to determine the crystalline phase, texture, and electronic structure of Hf1-xZrxO2 (x = 0-1) high-k gate dielectric thin films grown by atomic layer deposition using a cyclical deposition and annealing method. X-ray diffraction (XRD) analysis performed in both grazing incidence and pole figure configurations identified the tetragonal phase for Zr/(Zr + Hf)% = 58% and a concomitant increase in tetragonal phase for further increase in Zr content. X-ray absorption spectroscopy (XAS) was used to determine the local atomic structure and metal oxide bond orientation. Polarization dependent XAS in normal and grazing incidence showed preferential metal-oxygen bond orientation consistent with the texturing observed by XRD. X-ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE) were also performed with special focus on spectral features which arise as a consequence of atomic ordering and specific crystalline phase. The combination of XAS, XPS, SE, and XRD enabled the determination of the effects of the deposition scheme and compositional alloying on the electronic structure, crystal field effects, optical properties, crystal phase, and texture for the mixed oxide alloy series. The multi-technique approach revealed the martensitic-like transformation of crystalline phase from monoclinic to tetragonal as the majority metal oxide concentration in the alloy mixture changed from HfO2 to ZrO2. [ABSTRACT FROM AUTHOR]

Lattice spacing measurements of the (211)/(202), (020)/(013), and (111)/(102) reflections were used to calculate the residual stresses in a Ni monosilicide film after cooling from its formation temperature. The ability to measure stresses in crystalline materials using x-ray diffraction requires the use of appropriate x-ray elastic constants, which link the measured strain to the stress tensor of the grains that satisfy the diffraction condition. X-ray elastic constants were calculated in the Neerfeld–Hill (NH) limit for a polycrystalline aggregate composed of orthorhombic crystals. The anisotropy in grains that possess orthorhombic elasticity introduces significant variation in the stresses determined among the three sets of reflections. However, the in-plane stress calculated due to thermal expansion mismatch between NiSi and the underlying Si substrate shows a close correspondence to the average of x-ray measurements. [ABSTRACT FROM AUTHOR]

The texture of CoSi2 films on Si(001) substrates has been examined using synchrotron based high-resolution pole figure analysis. We find that axiotaxy, a recently recognized type of texture which was observed in NiSi thin films on Si(001), is also occurring in CoSi2 layers. Typical of axiotaxy texturing, the CoSi2 pole figures show symmetrical patterns of lines. Calculations show that these features on the pole figures are created by three off-normal fiberlike texture components. These off-normal fiber orientations are a consequence of the alignment of CoSi2<110> planes with Si<110> planes because of very similar d spacings, which causes a periodic arrangement along Si<100> directions in the plane of the interface. This one-dimensional periodicity may provide a lower interfacial energy; however, the periodic arrangement along the Si<100> directions may also be indicative of growth anisotropy. The influence of Ti alloying has been investigated by using in situ x-ray diffraction measurements, as well as pole figure analysis. These results show that the nucleation of both the CoSi and CoSi2 phases is delayed to higher temperatures for the 5 at. % Ti alloyed films. The texture of the CoSi2 phase is also influenced by the addition of Ti. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]