Proton-exchanged LiNbO/sub 3/ optical waveguides using stearic acid

Proton-exchanged optical waveguides have been fabricated in z-cut LiNbO/sub 3/ using a new proton source: stearic acid. These waveguides were characterized optically and were found to exhibit a step index profile with Delta n=0.118 measured at 0.633 mu m. The propagation losses were typically around 1.5 dB/cm, and the diffusion constant and the activation energy for the proton-exchange process were measured to be 5*10/sup 6/ mu m/sup 2//h and 69 kJ/mol, respectively.<>     

Proton-exchanged optical waveguides in LiNbO/sub 3/ using octanoic acid

Low-loss proton-exchanged planar waveguides in z-cut LiNbO/sub 3/ were fabricated and characterized optically using octanoic acid as a proton source. The waveguide exhibited a step-index profile with an index change of 0.118 measured at 0.633 mu m. The lowest waveguide propagation loss measured was 1.2 dB/cm, and it was reduced further to 0.4 dB/cm after annealing. The diffusion rate and the activation energy using this acid were found to be lower than those reported using other acids.<>     

Proton-exchange optical waveguides in Z-cut LiNbO/sub 3/ using toluic acid

Proton-exchanged planar waveguides were demonstrated in Z-cut LiNBO/sub 3/ using toluic acid as a new organic proton source. These waveguides exhibit a propagation loss of around 1 dB/cm, and a step refractive index profile with an index increase of 0.124 measured at 0.663 mu m. The diffusion rate was found to be lower than those obtained using the popular benzoic and phosphoric acids.<>     

Observation of femtosecond beats using Raman radiation from SiO/sub 2/ optical fibres

The authors have measured, using a forward four-wave mixing geometry, the 76 fs beat between two successive high-order Stokes components of Raman radiation from a silica-based optical fibre. The experimental results are in good qualitative agreement with theoretical calculations.<>     

An optical investigation of electronic excitations in the high temperature superconductors YBa/sub 2/Cu/sub 3/O/sub 7- delta / and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+ Delta /

The results of Raman scattering from superconducting gap excitations in the high T/sub c/ compounds YBa/sub 2/Cu/sub 3/O/sub 7- delta / and Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+ Delta / are compared. In the normal state, both materials exhibit strong electronic interband scattering which manifests itself as a broad background continuum having both A/sub 1g/ and B/sub 1g/ symmetry components. At low temperatures a redistribution of this electronic scattering occurs, indicative of the formation of a superconducting gap in these compounds. The two symmetries exhibit distinct redistribution, however, denoting strong anisotropy. At temperatures well below T/sub c/, both compounds exhibit residual low-energy scattering, a feature suggestive of the coexistence of normal electrons and superconducting quasi-particles.<>     

Optical activity induced in Bi/sub 4/Ge/sub 3/O/sub 12/ waveguides by ion implantation

The authors report data for ion implanted Bi/sub 4/Ge/sub 3/O/sub 12/ in which the modified material becomes optically active. The optical rotary power, after implantation and annealing, increases from zero to some 90 degrees /mm. The effect is attributed to an ion beam induced relaxation to a modified BiGeO phase.<>     

Metal-insulator-metal RF bypass capacitor using niobium oxide (Nb/sub 2/O/sub 5/) with HfO/sub 2//Al/sub 2/O/sub 3/ barriers

A high capacitance density (C/sub density/) metal-insulator-metal (MIM) capacitor with niobium pentoxide (Nb/sub 2/O/sub 5/) whose k value is higher than 40, is developed for integrated RF bypass or decoupling capacitor application. Nb/sub 2/O/sub 5/ MIM with HfO/sub 2//Al/sub 2/O/sub 3/ barriers delivers a high C/sub density/ of >17 fF//spl mu/m/sup 2/ with excellent RF properties, while maintaining comparable leakage current and reliability properties with other high-k dielectrics. The capacitance from the dielectric is shown to be stable up to 20 GHz, and resonant frequency of 4.2 GHz and Q of 50 (at 1 GHz) is demonstrated when the capacitor is integrated using Cu-BEOL process.     

Love-wave biosensors using cross-linked polymer waveguides on LiTaO/sub 3/ substrates

The design and performance of Love-wave sensors using crosslinked poly(methyl methacrylate) waveguides of thicknesses of 0.3 to 3.21 /spl mu/m on LiTaO/sub 3/ substrates are described. It is found that this layer-substrate combination provides sufficient waveguidance and electrical isolation of the interdigital transducers from the liquid environment to achieve low acoustic loss and distortion. In biosensing experiments, mass sensitivity up to 1420 Hz(ng/mm/sup 2/) is demonstrated.     

High-performance MIM capacitor using ALD high-k HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectrics

For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.     

Ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on surface-nitrided Ge

We have studied ultrathin Al/sub 2/O/sub 3/ and HfO/sub 2/ gate dielectrics on Ge grown by ultrahigh vacuum-reactive atomic-beam deposition and ultraviolet ozone oxidation. Al/sub 2/O/sub 3/-Ge gate stack had a t/sub eq//spl sim/23 /spl Aring/, and three orders of magnitude lower leakage current compared to SiO/sub 2/. HfO/sub 2/-Ge allowed even greater scaling, achieving t/sub eq//spl sim/11 /spl Aring/ and six orders of magnitude lower leakage current compared to SiO/sub 2/. We have carried out a detailed study of cleaning conditions for the Ge wafer, dielectric deposition condition, and anneal conditions and their effect on the electrical properties of metal-gated dielectric-Ge capacitors. We show that surface nitridation is important in reducing hysteresis, interfacial layer formation and leakage current. However, surface nitridation also introduces positive trapped charges and/or dipoles at the interface, resulting in significant flatband voltage shifts, which are mitigated by post-deposition anneals.     

Interfacial polarisation in Al-Y/sub 2/O/sub 3/-SiO/sub 2/-Si capacitor

The variation by a factor of 2 in the observed permittivity of yttrium oxide film is explained in terms of interfacial polarization based on the Y/sub 2/O/sub 3//SiO/sub 2/ double-layer model. Provided the dielectric relaxation time constants of the two layers are grossly dissimilar, the model can also explain the frequency independence of the composite capacitor.<>     

Index profile of proton-exchanged waveguides in LiNbO/sub 3/ using pyrophosphoric acid

A systematic study was carried out on proton-exchanged LiNbO/sub 3/ optical waveguides using pyrophosphoric acid. A maximum surface index increase of 0.145 was measured at 0.633 mu m for z-cut substrates. The index profile could be accurately modelled by a polynomial expression of simply by a 'truncated' step-index profile.<>     

GaN MOS device using SiO/sub 2/-Ga/sub 2/O/sub 3/ insulator grown by photoelectrochemical oxidation method

We report on a SiO/sub 2/-Ga/sub 2/O/sub 3/ gate insulator stack directly grown on n-type GaN by the photoelectrochemical oxidation method. The resultant MOS devices are fabricated using standard photolithography and liftoff techniques. The effect of annealing temperature on the SiO/sub 2/-Ga/sub 2/O/sub 3//n-type GaN MOS devices is investigated. The properties of high breakdown field, low gate leakage current, and low interface state density are investigated for the MOS devices.     

Characteristics of Al/sub 2/O/sub 3//TiO/sub 2/ nanolaminates and AlTiO thin films on Si

This letter reports a metal-insulator-semiconductor structure based on Al/sub 2/O/sub 3//TiO/sub 2/ nanolaminates and AlTiO films evaporated on an unheated p-Si substrate. The structure exhibits a low hysteresis in the capacitance-voltage characteristics, a larger dielectric constant leading to a quantum mechanically corrected effective oxide thickness of 1.35-2.1 nm, good stability of the electrical characteristics to thermal processes, a large breakdown electric field of 7.5 MV/cm, and a leakage current density below 5/spl times/10/sup -7/ A/cm/sup 2/ at an electric field of 2 MV/cm.     

Fully silicided NiSi gate on La/sub 2/O/sub 3/ MOSFETs

We have fabricated the fully silicided NiSi on La/sub 2/O/sub 3/ for n- and p-MOSFETs. For 900/spl deg/C fully silicided CoSi/sub 2/ on La/sub 2/O/sub 3/ gate dielectric with 1.5 nm EOT, the gate dielectric has large leakage current by possible excess Co diffusion at high silicidation temperature. In sharp contrast, very low gate leakage current density of 2/spl times/10/sup -4/ A/cm/sup 2/ at 1 V is measured for 400/spl deg/C formed fully silicided NiSi and comparable with Al gate. The extracted work function of NiSi was 4.42 eV, and the corresponding threshold voltages are 0.12 and -0.70 V for respective n- and p-MOSFETs. Electron and hole mobilities of 156 and 44 cm/sup 2//V-s are obtained for respective n- and p-MOSFETs, which are comparable with the HfO/sub 2/ MOSFETs without using H/sub 2/ annealing.     

Blue energy upconversion emission in thulium-doped-SiO/sub 2/-P/sub 2/O/sub 5/ channel waveguides excited at 1.064 /spl mu/m

Blue energy upconversion emission in Tm/sup 3+/-doped SiO/sub 2/-P/sub 2/O/sub 5/ channel waveguides off-resonance pumped by infrared radiation is reported. The waveguide samples were excited by a single continuous-wave laser source at 1.064 /spl mu/m. Two distinct blue emission signals around 450 and 480 nm, in addition to red at 660 nm and near-infrared at 800-nm less intense emissions were observed. The upconversion excitation mechanism was assigned to stepwise multiphoton absorption processes followed by nonradiative multiphonon-assisted relaxation processes. Infrared-to-blue conversion efficiencies with respect to the absorbed pump power of /spl sim/6.0/spl times/10/sup -7/ for this off-resonance pumping scheme was measured. The dependence of the infrared-to-blue upconversion mechanism upon the excitation power and thulium content is also examined.     

MIM capacitors using atomic-layer-deposited high-/spl kappa/ (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ dielectrics

Metal-insulator-metal (MIM) capacitors with (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ high-/spl kappa/ dielectric films were investigated for the first time. The results show that both the capacitance density and voltage/temperature coefficients of capacitance (VCC/TCC) values decrease with increasing Al/sub 2/O/sub 3/ mole fraction. It was demonstrated that the (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ MIM capacitor with an Al/sub 2/O/sub 3/ mole fraction of 0.14 is optimized. It provides a high capacitance density (3.5 fF//spl mu/m/sup 2/) and low VCC values (/spl sim/140 ppm/V/sup 2/) at the same time. In addition, small frequency dependence, low loss tangent, and low leakage current are obtained. Also, no electrical degradation was observed for (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ MIM capacitors after N/sub 2/ annealing at 400/spl deg/C. These results show that the (HfO/sub 2/)/sub 0.86/(Al/sub 2/O/sub 3/)/sub 0.14/ MIM capacitor is very suitable for capacitor applications within the thermal budget of the back end of line process.