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The cross section for electron photodetachment has been measured for the acetylide anion (HC2−) using an ion cyclotron resonance spectrometer in conjunction with a xenon arc lamp. Calculation of the photodetachment behavior near threshold and an estimate of the Franck–Condon factors for the anion→neutral transition allow us to determine EA (HC2⋅) = 2.94±0.10 eV. A theoretical determination using eighth-order perturbation theory gives an adiabatic electron affinity of 3.18±0.25 eV, in good agreement with the experimental result. The use of a thermochemical cycle with the experimental electron affinity and gas-phase acidity data gives a C–H bond dissociation energy in acetylene of 132±5 kcal/mol.

It has been determined that anodic oxidation of (Hg,Cd)Te occurs via a dissolution-precipitation mechanism followed by a bulk growth process which involves either interstitial transport of metal cations and/or hydroxyl anion transport via successive jumps. The initial film formation can be understood at least partially in terms of electrochemical parameters and, therefore, can be controlled in a rational manner. For example, stirring the anodization solution during dissolution prohibits film formation due to an increase in the rate of diffusion of ionic species away from the anode. MOS structures fabricated incorporating this electroetch in the passivation process show unique properties which provide evidence for a direct correlation between initial oxide formation and the resultant (Hg,Cd)Te surface electronic properties.

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Articles you may be interested inElectronic states and spin-orbit splitting of lanthanum dimer J. Chem. Phys. 135, 034309 (2011); 10.1063/1.3615505Laser photodetachment electron spectrometry of methoxide, deuteromethoxide, and thiomethoxide: Electron affinities and vibrational structure of CH30, CD30, and CH3SThe cross section for electron photodetachment has been measured for the thiomethoxyl anion (CH)S--) and the deuterothiomethoxyl anion (CD)S -) using an ion cyclotron resonance spectrometer in conjunction with a tunable dye laser. After accounting for the effective rotational broadening, these spectra yield the electron affinities, EA(CH)S) = 1.861±0.004 eV and EA(CD)S) = 1.858±0.OO6 eV. A doubling of features is observed in the photodetachment spectra which arises from transitions to the 2E312 and 2E\12 spin--{)rbit states of the final-state radicals. From these spacings we obtain a spin--{)rbit coupling constant (A) in CH)S' of -280±50 cm-I and in CD)S' of -260±50 em-I. The spectra also contain transitions to excited vibrational states of the radicals for which we obtain vibrational frequencies of 770+ 50 cm -I for the symmetric C-S stretching motion in CH)S (660±60 em -I in CD)S) and 1360± 70 em -I fur the methyl umbrella motion (\ 100±50 cm-I in CD)S).

We have demonstrated the controlled growth of photochemical native oxide on (Hg, Cd)Te by the UV photodissociation of N2O. The initial growth rate is ∼7Å/min, is insensitive to temperature over the range from 40 to 100 °C, and is dependent on the surface Hg concentration. Encapsulation of the native oxide with photochemical SiO2 results in a degradation of the (Hg, Cd)Te–native oxide interface electrical properties. The presence of photochemical HgO between the native oxide and SiO2 results in superior (Hg, Cd)Te surface electronic properties. However, MOS structures comprising SiO2 on a double layer of HgO on photochemical native oxide undergo an electrical degradation at room temperature, likely owing to reactions between HgO and the native oxide or (Hg, Cd)Te substrate.

GaAs quantum well infrared detectors with peak responsivity at 8.2 μm and significant response beyond 10 μm have been demonstrated with detectivities of 4×1011 cm (Hz)1/2 /W at 6 K; this detectivity is the highest reported for a quantum well detector. The detectors comprised 50 GaAs quantum wells of width 40 Å with an average Si doping density of 1×1018 cm−3 separated by 280-Å barriers of Al0.28Ga0.72As. In this design, the state to which electrons are excited by infrared absorption and from which they are subsequently collected lies in the continuum above the energy of the Al0.28Ga0.72As conduction-band minimum. The maximum detector responsivity was mesured to be 0.34 A/W. The device dark current density is 5.5×10−6 A/cm2 with the detector biased for maximum detectivity (3.5 V), and the dark current remains constant with increasing temperature up to 50 K. The detector noise current was observed to be a constant fraction (70%) of the shot noise down to noise currents of 10−14 A/(Hz)1/2. A theoretical model for the dark conduction process in a quantum well detector has been developed which successfully predicts the observed dark current noise.