Er3+ –Y3+-Codoped Al 2O3 for High-Temperature Sensing

Optical high-temperature sensing using the fluorescence intensity ratio (FIR) technique of green up-conversion emissions at 523 and 546 nm in Er³⁺-Y³⁺-codoped Al₂O₃ was studied in a wide temperature range of 295 K-973 K. The maximum sensitivity and the temperature resolution derived from the FIR technique are approximately 0.0035 K^-1 and 0.3 K, respectively, which indicated that Er³⁺-Y³⁺-codoped Al₂O₃ plays an important role for applications in the optical high-temperature sensing.     

Improved second-harmonic generation by selective Yb ion doping in anew nonlinear optical crystal YCa4O(BO3)3

We describe experiments characterizing a new nonlinear optical crystal, YCa₄O(BO₃)₃ (YCOB). This crystal has a number of advantages over other commonly available nonlinear optical crystals. It has a higher nonlinear coefficient than KDP, can be fabricated to large sizes (~3-in diameter, 8-in length), and has a high damage threshold. Moreover, this new nonlinear optical crystal is nonhygroscopic, has good optical quality and mechanical properties, allowing easy optical polishing. This crystal, YCa₄ O(BO₃)₃, commonly termed YCOB, is one of a family of new nonlinear crystals, the oxyborates, that include RECa₄O(BO₃)₃ (RE=La³⁺, La ³⁺, Y³⁺, Sm³⁺, Gd³⁺, Er³⁺, and Nd³⁺). In this paper, we also successfully demonstrate a technique for improving the nonlinear optical properties of this crystal. This technique, ion substitution, has previously had limited success with other crystal hosts. However, the inclusion of yttrium in YCOB provides the opportunity to exploit this technique. Yb³⁺, which has larger mass, but approximately the same atomic size as Y³⁺ can be substituted into the crystal structure without introducing stress and nonuniformities. A systematic investigation of the linear and nonlinear characteristics of several crystals doped with various levels of Yb demonstrate that selective substitution of Yb in YCa₄O(BO₃)₃ improves the second-harmonic conversion efficiency by increasing the optical nonlinearity     

Wideband Nonlinear Response of High-Temperature Superconducting Thin Films From Transmission-Line Measurements

We report on a technique for extracting an accurate value of the nonlinear inductance in superconducting transmission lines. This novel technique assesses the frequency dependence of the transmission line's nonlinear response. A wideband nonlinear measurement system was used to simultaneously measure the third-order spurious signals at 2f₁ - f_2, 2f₂ - f₁ + f₂, 2f₂ + f₁, 3f₁, and 3f₂ frequencies. Measurements for different values of the fundamental frequencies f₁ and f₂ allow us to study the spurious signal generation from 1 to 21 GHz. We demonstrate this technique by measuring several superconducting YBa₂Cu₃O_7-x coplanar waveguide transmission line geometries patterned in a single chip at 80 K. The results show a linear frequency dependence of the nonlinear response, indicating a dominant contribution of the nonlinear inductance over the nonlinear resistance omegaDeltaL(i) Gt DeltaR(i). The experimentally obtained nonlinear inductances are then used to determine device-independent measures of the linearity of the thin-film material in order to provide the foundation for modeling the nonlinear response of specific devices.     

A simplified capless annealing of GaAs for MESFET applications

A simple capless annealing technique for post-implantation annealing of a GaAs wafer is described. The technique incorporates a novel boat design and uses InAs as the source of arsenic overpressure. Using this technique, wafers annealed at 850°C show mobilities in the range of 4000 cm². V^-1. S^-1with over 85-percent activation for a Si dose of5 times 10^{12}cm^-2. Dopant depth profiles with peak donor densities of2 times 10^{17}cm^-3and minimal tailing were demonstrated. Electron channeling data show that crystallinity is fully restored during the anneal. 1-µm gate length MESFET's processed on n⁺-n implanted layers exhibitedg_{m} geq 160mS/mm and pinchoff voltages in the range of 3 V.     

A new open diffusion technique using evaporated Zn3P2and its application to a lateral p-n-p transistor

This paper reports a new open diffusion technique with a thin vacuum-deposited Zn3P2layer covered by an Al2O3layer. The diffusion in     

MOS characteristics of NH3-nitrided N2O-grownoxides

The technique of NH₃ nitridation of N₂O oxides is proposed and demonstrated for increasing nitrogen concentration in N₂O oxides so as to improve the resistance to boron penetration, without any adverse effects on electrical and reliability properties. Results show that NH₃-nitrided N₂O oxides exhibit excellent electrical (low fixed charge) and reliability (smaller charge trapping and suppressed interface state generation) properties, with an additional advantage of significantly improved resistance to boron generation. This technique may have a great impact on deep-submicrometer dual-gate CMOS technology     

Bulk and interface imperfections in semiconductors

Charges trapped at imperfection centers can be detected by observing the slow time dependences of the high-frequency small-signal capacitance and the current of a space charge region which is depleted of carriers. Detection of as low as 10¹⁰ to 10¹¹ trapped electron charges per cm³ in a volume of 10⁻³ cm × 10⁻³ cm², or 10⁵ to 10 electron charges, can be achieved. This technique has been used to study the temperature, electric field and photon energy dependences of the thermal, optical and Auger-impact emission and capture rates of electrons and holes at impurity and defect centers in depleted bulk and surface space charge regions in semiconductors, as well as the generation, annealing and diffusion kinetics of these centers. It has also been used to monitor the silicon integrated circuit fabrication processes. The principle of this technique is described and experimental examples are given to illustrate the applications of the technique.     

Sensitivity of Rs-measurement of HTS thin films by threeprime resonant techniques: cavity resonator, dielectric resonator, andmicrostrip resonator

The microwave surface resistance, R_s measurement of YBa ₂Cu₃0_{7 -δ} (YBCO) thin film deposited on 10 mm × 10 mm LaAlO₃ substrate using three prime resonating techniques, namely, cavity end plate substitution technique (20 GHz), dielectric resonator technique (18 GHz), and microstrip resonator technique (5 GHz), is reported. In addition, theoretical analysis for each technique has been performed to calculate the relative percentage error in the measured R_s -value of the YBCO thin film as a function of temperature. It has been found that the shielded dielectric resonator provides far better sensitivity for R.-measurement of the YBCO thin film with minimum relative percentage error (<4%) in the temperature range from 20 K to transition temperature of YBCO thin film compared to the other two techniques     

Diffusion profiling using the graded C(V) method

A simple and quick technique for determination of impurity-diffusion profiles in semiconductors from MOSC(V)measurements on a gradually etched surface is presented and analyzed, This technique is most useful for slowly varying profiles in the range of 10¹⁶-5 × 10¹⁸cm^-3. Experimental profiles are given for P in Si, and for Cd in InSb.     

C2F6reactive ion-beam etching of LiNbO3and Nb2O5and their application to optical waveguides

Properties of C2F6(freon 116) reactive ion-beam etching (RIBE) of LiNbO3, Ti-indiffused LiNbO3, and sputter-deposited Nb2O5film on LiNbO3are reported. A maximum differential etching ratio of approximately 5:1 has been measured for LiNbO3and the AZ 1350B Shipley photoresist. We have used this etching technique to fabricate diffraction gratings on both Ti-indiffused LiNbO3and Nb2O5- LiNbO3waveguides with measured throughput efficiencies in excess of 85 percent.     

Lateral tunneling transistors fabricated by plane-dependent Si-doping in nonplanar epitaxy on GaAs (311)A and (411)A substrates

We have demonstrated the lateral tunneling transistors on GaAs (311)A and (411)A patterned substrates by using the plane-dependent Si-doping technique. Lateral p⁺-n⁺ tunneling junctions are formed by growing heavily Si-doped layers on patterned substrates. Current—voltage curves for both transistors show gate-controlled negative differential resistance characteristics. Furthermore, the peak current density of the lateral tunneling diodes fabricated on the (311)A patterned substrates increases as buffer layer thickness is increased, and a typical peak current density of 58 A/cm² for p = 6 × 10¹⁹ cm⁻³ and n = 7 × 10¹⁸ cm⁻³ is obtained when the buffer layer thickness is 1.2 μm. This study shows that plane-dependent Si-doping in non-planar epitaxy is a promising technique for fabricating tunneling transistors.     

Initiation of NF3-H2chemical reactions via CO2laser irradiation of NF4BF4

NF4BF4has been irradiated with a low-power CO2laser to produce reactive species which then initiate reactions in an ambient NF3-H2mixture. The laser-induced decomposition of NF4BF4in vacuum was measured as a function of laser power and energy. The laser-induced decomposition threshold was determined to be 40 mJ, which corresponds to a laser fluence of 20 J/cm². This same value was determined for the initiation threshold of NF3-H2reactions via CO2laser irradiation of NF4BF4. Visible and infrared emissions were observed from initiated NF3-H2mixtures. This radiative technique has attractive features for initiating reactions in solid-gas systems.     

Gain limitations in TE CO2laser amplifiers

The factors which limit the small-signal gain of TE CO2laser amplifiers are investigated with a novel technique based on gain measurements of the sequence, hot, and regular CO2laser bands. This new technique enables us, for the first time, to determine accurately and independently the rotational and vibrational temperatures characterizing the CO2laser system. The gain ratio of the sequence band (00° 2) to the regular band (00° 1) provides a simple and accurate determination of the ν3mode vibrational temperature. It is found experimentally that the ν3mode vibrational temperature saturates at a high input discharge energy. This saturation sets an upper limitation to the gain attainable in TE CO2laser amplifiers. As we can measure all the characteristic temperatures relevant to the gain medium, a detailed comparison between the calculated and experimental gain can be carried out with no variable parameters. The result of such a direct comparison confirms both the validity of the conventional "mode temperature" model for CO2laser dynamics and the validity of our measurement technique for vibrational temperatures.     

A digital technique for the measurement of power losses in hightemperature superconductors

A digital power loss measurement technique that enables the fast and accurate measurement of AC power losses in superconductors is described. This technique allows loss measurements at all frequencies limited only by the maximum sampling rate and buffer memory of the digital measuring device. Using the digital technique, power loss measurements on YBa₂Cu₃O₇ are compared to similar measurements using the analog wattmeter     

The effects of annealing step-edges on SrTiO3 and MgOsingle-crystal substrates on YBa2Cu3O7Josephson junctions

The effect of annealing step-edges on SrTiO₃ and MgO single-crystal substrates on Josephson junctions of YBa₂Cu ₃O₇, has been studied. The step-edge was fabricated by argon-ion milling technique and was annealed at 1050°C in oxygen atmosphere. YBa₂Cu₃O₇ thin film was deposited on the annealed step-edge by a standard pulsed laser deposition. The effect of annealing the step-edge on the junction was characterized by AFM and current-voltage (I-V)characteristic. The annealed step-edge on SrTiO₃ and MgO substrates showed that the surface of the substrates was smoother and I-V characteristic of Josephson junction improved     

Formation of high quality storage capacitor dielectrics by in-siturapid thermal reoxidation of Si3N4 films inN2O ambient

This letter reports on a novel reoxidation technique for SiO₂ /Si₃N₄ (ON) stacked films by using N₂ O as oxidant. Effect of in-situ rapid thermal N₂O reoxidation (RTNO) on the electrical characteristics of thin ON stacked films are studied and compared with those of in-situ rapid thermal. O ₂ reoxidation (RTO). Prior to reoxidation, the Si₃N₄ film was deposited by rapid thermal chemical vapor deposition (RT-CVD) using SiH₄ and NH₃. Results show that RTNO of the Si₃N₄ films significantly improves electrical characteristics of ON stacked films in terms of lower leakage current, suppressed charge trapping, reduced defect density and improved time-dependent-dielectric-breakdown (TDDB), as compared to RTO of the Si₃N₄ films     

Thermal and Optical Properties of Yb3+- and Nd3+-Doped Phosphate Glasses Determined by Thermal Lens Technique

In this work, we study the thermal and optical properties of ion-doped phosphates glasses using the thermal lens (TL) technique. Three samples were characterized: Nd³⁺-doped Q-98; Nd³⁺-doped Q-100; and Yb³⁺-doped QX. We report multiwavelength TL measurements for a more accuracy determination of the fluorescence quantum efficiency and temperature coefficient of the optical path length change (ds/dT). In Nd-doped glasses, it was carried out using four discrete excitation wavelengths (between 514 and 872 nm) chosen to match with the ion absorption lines. In Yb-doped glass, the spectrum of heat generated along the Yb³⁺ transition (² F _5/2rarr² F _7/2) was obtained. In addition, parameters as thermal diffusivity and conductivity, thermal loading, etc were achieved. The advantages to obtain fluorescence quantum efficiency using the TL technique, mainly in Yb³⁺ doped materials, which are normally overestimated due to radiation trapping effect, are presented. The accuracy knowledge of these parameters is very important for design of high-power solid-state lasers, since these properties are directly related to the heat generation.     

Transport properties of Mn-doped Ru2Si3

Transport properties of Mn-doped ruthenium silicide Ru₂Si₃ were studied both experimentally and theoretically. The precipitation-free Ru₂Si₃ single crystals were grown by the zone melting technique with radiation heating. The temperature dependence of the electrical resistivity and Hall coefficients of the crystals were measured. The electrical resistivity of 1% Mn-doped Ru₂Si₃ was lower than that of undoped crystals. The carrier concentration in the doped samples is about 10¹⁸ cm⁻³ at room temperature. Mn-doped Ru₂Si₃ has a twice higher carrier mobility compared to the undoped one. Theoretical calculation of the charge carrier mobility is based on the effective masses which are estimated from the ab initio electronic band structure and classical scattering mechanisms.     

Nitridation and post-nitridation anneals of SiO2 forultrathin dielectrics

A technique of post-oxidation annealing to improve the properties and long-term reliability of ultrathin (<100 Å) MOS gate dielectrics is discussed. In this technique, after oxidation, nitridation is done in NH₃, followed by a light reoxidation in O₂, and then an inert anneal in Ar or N₂. Using this technique, both optimum performance and reliability can be obtained without sacrificing either. NH₃ anneal of SiO₂ improved the hot-electron immunity, but degraded the interface quality. Good properties could be obtained by a strong reoxidation of the nitrided films, at the expense, however, of a substantial increase in the film thickness. Nitrogen and argon ambients were found to be equally effective at improving film properties. By annealing the film in an inert ambient following reoxidation of the nitroxide, fixed charge can be further decreased with little oxide grown, electron mobility in NMOS FETs increases further, and the hot-electron lifetime is much longer than that of the starting oxide     

LaNiO3: a promising material for contact with YBa2Cu3O7-x thin films

Epitaxial LaNiO₃ metallic oxide thin films have been grown on c-axis oriented YBa₂Cu₃O_7-δ thin films on LaAlO₃ substrates by pulsed laser deposition technique and the interface formed between the two films has been examined by measuring the contact conductance of the same. The specific contact conductance of the interface measured using a modified four probe method was found to be 1.4 to 6×10⁴ ohm^-1 cm^-2 at 77 K. There are indications that contact conductance can be brought closer to that obtained for noble metal-YBCO interface