Invited; Contact effects towards mainstream thin-film transistor applications

Thin-film source-gated transistors (SGTs) [1] have been developed steadily over the last couple of decades, demonstrating important properties which span virtually all thin-film material systems [2], [3]. By virtue of their control mechanism, which relies on an energy barrier deliberately engineered at the source, they present impressive intrinsic gain [4], [5], tolerance to variability [6], stability [7], and temperature sensing utility [8]. Recently, numerous groups have adopted the architecture [2], [3] and conceptual evolutions have led to new and highly functional TFT devices [9]–[11]. As the contact-controlled nature of these transistors introduces a relatively large temperature dependence of drain current, and also drastically reduces the current density, for a given geometry, recent research (Fig. 1-3) is focusing on shifting the balance away from these limitations [12]–[14], without compromising the structure’s advantages. Please click Download on the upper right corner to see the full abstract

Novel Tunnel-Contact-Controlled IGZO Thin-Film Transistors with High Tolerance to Geometrical Variability.

Thin insulating layers are used to modulate a depletion region at the source of a thin-film transistor. Bottom contact, staggered-electrode indium gallium zinc oxide transistors with a 3 nm Al2 O3 layer between the semiconductor and Ni source/drain contacts, show behaviors typical of source-gated transistors (SGTs): low saturation voltage (VD_SAT ≈ 3 V), change in VD_SAT with a gate voltage of only 0.12 V V-1 , and flat saturated output characteristics (small dependence of drain current on drain voltage). The transistors show high tolerance to geometry: the saturated current changes only 0.15× for 2-50 µm channels and 2× for 9-45 µm source-gate overlaps. A higher than expected (5×) increase in drain current for a 30 K change in temperature, similar to Schottky-contact SGTs, underlines a more complex device operation than previously theorized. Optimization for increasing intrinsic gain and reducing temperature effects is discussed. These devices complete the portfolio of contact-controlled transistors, comprising devices with Schottky contacts, bulk barrier, or heterojunctions, and now, tunneling insulating layers. The findings should also apply to nanowire transistors, leading to new low-power, robust design approaches as large-scale fabrication techniques with sub-nanometer control mature

VARIANTS FOR EVALUATING THE RIGIDITY OF FLAT RING FLANGES

This paper describes an analytical way of comparative evaluation of the stiffnesses developed in assemblies with flat ring flanges, of optional type, welded to the cylindrical body of a pressure vessel. Based on the theory of the compatibility of deformations (radial displacements and rotations), the mathematical expressions necessary for the evaluation of the unitary radial bending moments and the unitary shearing forces of connection are established. With their help, the values of the rotation angles of the rings can be calculated and compared with the admissible ones. The present analysis considers the quantitative effect of the deformed gasket and the stiffness of the curved/bent screws on the tightness of the system. The methodology is flexible by introducing some selection factors, so that the mentioned influences can be easily separated and compared

VARIANTS FOR EVALUATING THE RIGIDITY OF FLAT RING FLANGES

This paper describes an analytical way of comparative evaluation of the stiffnesses developed in assemblies with flat ring flanges, of optional type, welded to the cylindrical body of a pressure vessel. Based on the theory of the compatibility of deformations (radial displacements and rotations), the mathematical expressions necessary for the evaluation of the unitary radial bending moments and the unitary shearing forces of connection are established. With their help, the values of the rotation angles of the rings can be calculated and compared with the admissible ones. The present analysis considers the quantitative effect of the deformed gasket and the stiffness of the curved/bent screws on the tightness of the system. The methodology is flexible by introducing some selection factors, so that the mentioned influences can be easily separated and compared

Current Status and Opportunities of Organic Thin-Film Transistor Technologies

Ajudes: National Key Research and Development Program of "Strategic Advanced Electronic Materials" under Grant 2016YFB0401100 and in part by the NSFC of China under Grant 61274083 and Grant 61334008.Attributed to its advantages of super mechanical flexibility, very low-temperature processing, and compatibility with low cost and high throughput manufacturing, organic thin-film transistor (OTFT) technology is able to bring electrical, mechanical, and industrial benefits to a wide range of new applications by activating nonflat surfaces with flexible displays, sensors, and other electronic functions. Despite both strong application demand and these significant technological advances, there is still a gap to be filled for OTFT technology to be widely commercially adopted. This paper providesa comprehensive reviewof the current status of OTFT technologies ranging from material, device, process, and integration, to design and system applications, and clarifies the real challenges behind to be addressed