Electrical conduction in chalcogenide glasses of phase change memory App. Phys. Rev. 2012, 8 (2012 Understanding the multistate SET process in Ge-Sb-Te-based phase-change memory J. Appl. Phys. 112, 064901 (2012) Highly sensitive tactile sensors integrated with organic transistors Appl. Phys. Lett. 101, 103308 (2012) Highly sensitive tactile sensors integrated with organic transistors APL: Org. Electron. Photonics 5, 206 (2012) On the nature of the interfacial layer in ultra-thin TiN/LaLuO3 gate stacks Amorphous chalcogenides have been extensively studied over the last half century due to their application in rewritable optical data storage and in non-volatile phase change memory devices. Yet, the nature of the observed non-ohmic conduction in these glasses is still under debate. In this review, we consolidate and expand the current state of knowledge related to dc conduction in these materials. An overview of the pertinent experimental data is followed by a review of the physics of localized states that are peculiar to chalcogenide glasses. We then describe and evaluate twelve relevant transport mechanisms with conductivities that depend exponentially on the electric field. The discussed mechanisms include various forms of Poole-Frenkel ionization, Schottky emission, hopping conduction, field-induced delocalization of tail states, space-charge-limited current, field emission, percolation band conduction, and transport through crystalline inclusions. Most of the candidates provide more or less satisfactory fits of the observed non-linear IV data. Our analysis calls upon additional studies that would enable one to discriminate between the various alternative models. V C 2012 American Institute of Physics. [http://dx.

Atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) using Surfx Atomflow(TM) 250D APPJ was utilized to synthesize amorphous silicon carbonitride coatings using tetramethyldisilizane (TMDZ) and hexamethyldisilizane (HMDZ) as the single source precursors. The effect of precursor chemistry and substrate temperature (T(s)) on the properties of a-SiCN:H films were evaluated, while nitrogen was used as the reactive gas. Surface morphology of the films was evaluated using atomic force microscopy (AFM); chemical properties were determined using Fourier transform infrared spectroscopy (FTIR); thickness and optical properties were determined using spectroscopic ellipsometry and mechanical properties were determined using nanoindentation. In general, films deposited at substrate temperature (T(s)) < 200 °C contained organic moieties, while the films deposited at T(s) > 200 °C depicted strong Si-N and Si-CN absorption. Refractive indices (n) of the thin films showed values between 1.5 and 2.0, depending on the deposition parameters. Mechanical properties of the films determined using nanoindentation revealed that these films have hardness between 0.5 GPa and 15 GPa, depending on the T(s) value. AFM evaluation of the films showed high roughness (R(a)) values of 2-3 nm for the films grown at low T(s) (<250 °C) while the films grown at T(s) ≥ 300 °C exhibited atomically smooth surface with R(a) of ~0.5 nm. Based on the gas-phase (plasma) chemistry, precursor chemistry and the other experimental observations, a possible growth model that prevails in the AP-PECVD of a-SiCN:H thin films is proposed.

Amorphous hydrogenated silicon carbonitride (a‐SiCN:H) thin films are synthesized by atmospheric pressure plasma enhanced chemical vapor (AP‐PECVD) deposition using the Surfx Atomflow™ 250D APPJ source with triethylsilane (HSiEt3, TES) and nitrogen as the precursor and the reactive gases, respectively. The effect of the substrate temperature (Ts) on the growth characteristics and the properties of a‐SiCN:H films was evaluated. The properties of the films were investigated via scanning electron microscopy (SEM), atomic force microscopy (AFM) for surface morphological analyses, Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS) for chemical and compositional analyses; spectroscopic ellipsometry for optical properties and thickness determination and nanoindentation to determine the mechanical properties of the a‐SiCN:H films. Films deposited at low Ts depict organic like features, while the films deposited at high Ts depict ceramic like features. FTIR and XPS studies reveal that an increases in Ts helps in the elimination of organic moieties and incorporation of nitrogen in the film. Films deposited at Ts of 425 °C have an index of refraction (n) of 1.84 and hardness (H) of 14. 8 GPa. A decrease in the deposition rate between Ts of 25 and 250 °C and increase in deposition rate between Ts of 250 and 425 °C indicate that the growth of a‐SiCN:H films at lower Ts are surface reaction controlled, while at high temperatures film growth is mass‐transport controlled. Based on the experimental results, a potential route for film growth is proposed.

We present a model of data retention for phase change memory devices in which the active medium is a thin layer of chalcogenide glass. Data retention capability is compromised when a crystalline path is spontaneously formed in the glassy host, essentially shunting the device. We determine the probability and statistics of device failure for systems in which the crystalline volume fraction is below the critical volume fraction of percolation theory. In that regime, we show that rectilinear crystalline path formation is favored and we determine the criteria for when such paths dominate over the typical percolation cluster scenario. Our analytical approach, based on modeling the formation of such paths in terms of a half-space random walk, leads to closed form expressions that relate data retention characteristics to device parameters. The model is used to examine the effects of device geometry, temperature, and external fields. The temporal statistics of device reliability are also considered for several failure mechanisms. A computer simulation is employed that supports our derived relationships between failure probability and device parameters.

We present a theory of second phase conductive filaments in phase transformable systems; applications include threshold switches, phase change memory, and shunting in thin film structures. We show that the average filament parameters can be described thermodynamically. In agreement with the published data, the predicted filament current voltage characteristics exhibit negative differential resistance vanishing at high currents where the current density becomes a bulk material property. Our description is extendible to filament transients and allows for efficient numerical simulation