Effect Of Dopant Diffusion Research Articles

Effect of Dopant Diffusion on the Long-Term Stability of Fabry–Pérot Optical Fiber Sensors

We present a research to determine the long-term stability of intrinsic Fabry–Perot (F–P) optical fiber sensors in high-temperature environments. In-fiber sensors were created in 125 μ m diameter single mode fiber (Corning SMF28 Ultra) and a 125 μm diameter PCF ESM-12B pure SiO2 fiber spliced to a SMF28 fiber with a low reflectivity Cr layer at the interface. The outcome is a low finesse optical cavity either formed by a short length of Ge doped SMF fiber, or a short length of pure and undoped SiO2 core PCF fiber. We demonstrate the manufacturing technique required for these intrinsic F–P sensors as well as the stability of their optical characteristics at temperatures up to the range of 850 °C to 1050 °C. We report on the effect of annealing on stability after exposing sensors to temperatures of 1000 °C above nominal working temperatures. In the temperature range above 900 °C we observe increasing levels of nonreproducible drift characteristics. Stability is demonstrated up to 1000 °C. After extended exposure of sensors to high temperatures we observe deviations from the initial smooth second-order response of phase versus temperature, which has been attributed to a change in core diameter in the fiber leading to the sensor at the distal end due to Ge diffusion at the high temperatures. The down lead is exposed to over a length of 17 cm. The dopant diffusion of an SMF28 ultra fiber has been studied using Energy Dispersive X-rays analysis (SEM/EDX), to measure the radial distribution of Ge concentration before and after being heated for a period of 100 days.

23.4: Photoemission Investigation of Cesium‐Doped tris(8‐hydroxyquinoline) aluminum (Alq3) and the Effect of Dopant Diffusion

AbstractThe chemical and electronic effects of Cs‐doped Alq3 have been investigated using X‐ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). XPS reveals the formation of a new nitrogen species shifted to lower binding energy that increases in intensity as a function of Cs doping. UPS reveals the formation of a new gap state in the previously forbidden band gap of Alq3 after Cs doping. Both results are consistent with the formation of a Cs‐Alq3 charge‐transfer complex. The thermal stability of the charge‐transfer complex was also evaluated using angle‐resolved XPS (ARXPS). The XPS data suggests that one Cs atom attached to an Alq3 molecule is thermally stable, but the addition of a second or third Cs atom to an Alq3 molecule produces a thermally unstable complex. OLED device data also confirms the thermal instability of the Cs‐Alq3 complex.

Dopant diffusion in [formula omitted] poly gate CMOS process

n + p + Poly gate CMOS devices were fabricated by a process modified from the “Twin-Tub V” CMOS ( n + poly gate) processing technology, using source-drain implants for polysilicon doping. CMOS devices so fabricated show comparable characteristics to devices fabricated by the Twin-Tub V process. The effect of dopant diffusion, both vertical and lateral, was studied in terms of several S/D implant anneal temperatures, 850–950°C. After high-temperature anneal, boron penetration from gate to the silicon resulted in depletion-mode characteristics in the p channel device. Lateral diffusion was observed for all processing conditions used. However, it was shown that when p + and n + poly gates are doped homogeneously above the degenerate level, the compensation effect from the counter doping by the diffused-in dopant does not cause measurable variations in the threshold voltage.

Tolerance requirements for dispersion free single-mode fiber design: Influence of geometrical parameters, dopant diffusion, and axial dip

The dispersion sensitivity to small changes in index-differences, radius, and wavelength is investigated in the case of dispersion free single-mode fibers. If a minimum bandwidth is required, tolerances on the various parameters can then be deduced: singly- and doubly-clad structures are compared. Constant reference is made to the HE 11 mode spot-size to relate dispersion properties and attenuation. A nonzero fundamental mode cutoff is shown to induce an enhanced sensitivity to a change in fiber geometrical characteristics. The effect of dopant diffusion and axial dip on dispersion is then considered and conclusions are drawn concerning the use of profiles measured on preforms to predict fiber propagation properties.

Tolerance Requirements for Dispersion Free Single-Mode Fiber Design: Influence of Geometrical Parameters, Dopant Diffusion, and Axial Dip

The dispersion sensitivity to small changes in index-differences, radius, and wavelength is investigated in the case of dispersion free single-mode fibers. If a minimum bandwidth is required, tolerances on the various parameters can then be deduced: singly- and doubly-clad structures are compared. Constant reference is made to the HE/sub 11/ mode spot-size to relate dispersion properties and attenuation. A nonzero fundamental mode cutoff is shown to induce an enhanced sensitivity to a change in fiber geometrical characteristics. The effect of dopant diffusion and axial dip on dispersion is then considered and conclusions are drawn concerning the use of profiles measured on preforms to predict fiber propagation properties.

GaAs-AlGaAs tunnel junctions for multigap cascade solar cells

The growth and characterization of tunneling GaAs homojunctions and GaAs-AlGaAs heterojunctions by molecular beam epitaxy for use as optically transparent interconnects in GaAs and AlGaAs solar cells is described. GaAs tunneling interconnects have been achieved with conductances of 300 A/cm2-V at 0.050 V, and p-AlxGa1−x As/n-GaAs heterojunction structures with x up to 0.4 have been grown which have characteristics comparable to GaAs interconnects. Thin interconnects, 1000 Å total thickness, have also been fabricated with conductances comparable to thicker junctions. The effect of dopant diffusion was found to be minimal at the 580 °C junction growth temperature, but annealing these tunnel junctions at 650 °C for several minutes caused diffusion of about 100 Å distance.