Large Angle Tilt Research Articles

New Large Angle Tilt Implanted Drain Structure: Surface Counter-Doped-Lightly Doped Drain for High Hot Carrier Reliability

A new surface counterdoped-lightly doped drain (SCD-LDD) structure with large angle tilt (LAT) implantation is proposed in this study. This structure introduces an additional larger tilt angle and lower-energy BF2 implant after the n- implant, which counterdopes the n- surface concentration to achieve a gate/ n- fully overlapped, buried and sloped n- region inside the gate edge. As a result, the lateral electric fields inside the gate edge are reduced and pushed deeper into the substrate. In addition to a reduction in substrate current, this profile also suppresses hot carrier injection by driving the current away from the surface and the maximum electric field; then it shifts the avalanche region further into the bulk Si. This consequently produces a more effective enhancement of hot carrier reliability than that of conventional LDD's and controlled large-angle-tilt implanted drains (LATID's) for submicron VLSI circuits under 5 V operation. In conclusion, this SCD-LDD provides one more degree of freedom in optimizing the n- region doping profiles as a new LATID structure.

An HREM investigation of the structure and defects in TiMnSi 2

Structure of and defects in TiMnSi 2 intermetallic compound were studied by high resolution electron microscopy (HREM). The reassembled reciprocal lattice from two sets of electron diffraction (ED) patterns obtained by large angle tilt test shows that TiMnSi 2 has an orthorhombic structure with space group Pbam. The atomic image of TiMnSi 2 viewed along the [001] zone direction has a tessellation of 3 2434 type, close to that of the “pentagon-sigma” phase. The (010) planar faults designated U (upward) and D (downward) are identified. The TiMnSi 2 structure and its defects are also verified by computer image simulation, and confirmed the results proposed earlier based on X-ray diffraction analysis.

Josephson-like properties of YBa/sub 2/Cu/sub 3/O/sub 7/ thin film weak links

Thin-film YBa/sub 2/Cu/sub 3/O/sub 7/ microbridges have been fabricated by photo- and e-beam lithography in polycrystalline thin films grown on MgO substrates and containing a controlled density of large-angle tilt boundaries, thereby isolating individual tilt-boundary weak links. Depending on the growth parameters of the film, such weak links have critical current densities J/sub c/ ranging from 10/sup 6/ A mod cm/sup 2/. The higher J/sub c/ microbridges exhibit behavior indicative of one-dimensional flux flow and flux creep in the weak links, while the lower J/sub c/ microbridges have RSJ-like properties. Detailed comparisons have been made between the predictions of the resistively shunted junction (RSJ) model including the calculated effects of thermal noise rounding and the measured DC and microwave response of these weak links. Measurements have also been made of magnetic field effects on the critical current density. An unexpected scaling behavior has been observed in the I-V characteristics of certain types of these microbridges containing 45 degrees tilt boundaries that indicates that in those cases I/sub C/R/sub N//sup 2/ is a constant for the tilt-boundary weak link. The implications of these results for developing a successful description of the superconductive properties of YBa/sub 2/Cu/sub 3/O/sub 7/ grain boundary weak links, which electron microscopy reveals to be clean, stoichiometric, and abrupt, are discussed.

Growth of YBa2Cu3O7 thin films on MgO: The effect of substrate preparation

We discuss the results of a study of the effect of substrate preparation on the microstructure and superconductive properties of YBa2Cu3O7 thin films formed by laser ablation on (001) MgO substrates. Thermal annealing of the substrates is found to be highly effective in producing at fairly low growth temperatures (670 °C), epitaxial, c-axis normal films with good superconductive properties. Alternative surface treatments result in the formation of large angle tilt boundaries and inferior superconductive properties.

Scaling behavior of YBa2Cu3O7−δ thin-film weak links

The superconductive weak link properties of microbridges formed in c-axis normal YBa2Cu3O7−δ polycrystalline thin films containing a variable amount of large angle tilt boundaries have been studied. In the low critical current density limit these weak links have current-voltage (I-V) characteristics that are accurately modeled by the resistively shunted junction model. The I-V’s are found to accurately follow a simple scaling law with the product of the critical current and weak link resistance Rn varying linearly with the weak link conductance.

Atomic Structure of Tilt Grain Boundaries in NiO

High-resolution electron microscopy at 400 kV has been used to study the core structure of large-angle tilt grain boundaries in NiO. The deduced atomic structures show considerable variety and complexity, even for boundaries with the same tilt axis and misorientation. The coexistence of asymmetric and symmetric boundaries which is observed at each misorientation suggests that asymmetric grain boundaries containing densely packed planes are associated with relatively low free energies. A multiplicity of core structures is found for the =5 and the =13 grain boundaries. The normal component of the rigid-body translation in these boundaries is quite small in view of the relatively open structure that is expected for grain boundaries in ionic solids. Substantial concentrations of Schottky pairs near the boundary cores, as well as relaxations parallel to the misorientation axis, are indicated. 11 refs., 7 figs.

Burgers vectors of dislocations in deformed iron and iron alloys

A new two beam dark field electron microscope technique has been applied to the determination of the Burgers vectors of dislocations in thin foils of high purity iron, Fe-0-75 % Mn alloy and 2¼ % Cr-1% Mo steel. The experimental technique and the design of a new large angle tilt goniometer specimen stage are described. Specimens have been deformed over a range of temperatures from — 117 to 600 °C at strain rates between 0-18 and 15 % per hour. Relatively large proportions of a <100> and a <110> type dislocations in addition to the expected 1/2 a <111> type dislocations have been found and their screw-edge characters and directions investigated. The work has shown that the simple ideas involving only 1/2 a <111> type dislocations intersecting to form a <(100)> type junctions in body-centred cubic metals have to be considerably modified.

The dislocation content of a large angle tilt boundary

Abstract Explicit formulae for the dislocation content of a large angle tilt boundary in a cubic crystal are presented. These are obtained by using the surface dislocation formalism modified to allow for the appropriate group symmetry of the crystal. The results are compared with a simple formula recently proposed by Sleeswyk.

The grain boundary energy and configuration of inert gas crystals—II

The expression derived in the previous paper (1) (hereafter referred to as (1)) for the average inverse power potential energy of interaction between a particle at a fixed distance above a half-crystal face and the half-crystal is applied to a calculation of the minimum energy spacing and interfacial energy between two perfect half-crystals placed together to form a “completely misfitting” grain boundary. The grain boundary energies and spacings of various juxtiposed surfaces of face-centered cubic argon at 0°K are calculated as examples with the following results in ergs cm 2 : (100)–(110), 41.7; (100)–(111), 22.8; (111)–(111), 16.0. This method would seem to be applicable to any system obeying the specified type of potential function when there is a continuous spontaneous generation of dislocations in two dimensions at the boundary as appears to be the case for large angle twist or tilt boundaries.