Pronounced 10(4)-fold enhancement of Raman scattering has been obtained for ZnO nanocrystals on substrates coated with 50 nm Ag nanoparticles under nonresonant excitation with a commercial red-emitting laser. This makes feasible beyond 10(-18) mole detection of ZnO nanocrystals with a commercial setup using a 0.1 mW continuous wave laser and can be purposefully used in analytical applications where conjugated nanocrystals serve as Raman markers. For Au-coated surfaces the enhancement is much lower and the heating effects in the course of Raman experiments are pronounced.

The interaction of electrons and phonons is strongly enhanced in ultrashort-period GaAs/AlAs superlattices. The enhancement is caused by an increase of the exciton binding energy with decreasing superlattice period. The photoluminescence spectra of indirect-gap superlattices exhibit a zero-phonon line due to scattering by defects and/or interfacial roughness as well as pronounced phonon sidebands. ͓S0163-1829͑97͒07015-X͔

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Silicon is the most commonly employed optoelectronic material, thanks to its high performance, long lifetime, and economic viability. [7,8] However, some fields of photodiodes' possible applications require additional features besides the excellent performance characteristics provided by conventional silicon photodiodes. [9,10] Rapid development of commercial and scientific space programs and large-scale nuclear safety efforts in radioactively contaminated areas presupposes the development of next-generation radiation-resistant optoelectronic materials and devices. [11][12][13][14][15][16] It is known that wide bandgap II-VI compound semiconductors possess a noticeably higher radiation resistance compared to their established commercially available counterparts Ge, Si, and III-V compounds. [17][18][19] For instance, the development of CdTe-base optoelectronic devices has been an active research field for years motivated by the demand for improved radiation hardness. [20][21][22][23] However, CdTe still exhibits only moderate radiation hardness that needs to be improved further to achieve reliable operation in harsh environments. [24,25] It has been shown that Cd 1−x Zn x Te solid solutions (also referred to as CdZnTe) possess much higher radiation resistance than CdTe. [26][27][28][29] As such, CdZnTe is commonly used as the active material for X-and γ-ray detectors. [30,31] The large A novel high-performance ultraviolet-visible-near-infrared (300-820 nm) heterojunction photodiode based on radiation-resistant semiconductor materials is proposed. A titanium nitride (TiN) "window" layer is deposited via magnetron sputtering onto a cadmium zinc telluride (CdZnTe) solid solution single crystal. The TiN/CdZnTe heterojunction photodiodes concurrently reveal an outstanding detectivity, response time, and linear dynamic range outperforming similar heterojunction photodiodes and photodetectors, based on photoactive inorganic compound semiconductor materials. Moreover, the added feature of the proposed heterojunction photodiodes is their excellent radiation resistance, experimentally demonstrated under short impulse proton irradiation (170 keV) with an accumulated fluence of 2 × 10 12 proton cm −2 . This unusual synergy of high performance and advanced radiation resistance of the TiN/CdZnTe photodiodes provides a unique platform for operation in space or radioactively contaminated environments.

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The transition from an indirect to a direct energy band structure has been induced in short-period GaAs/AlAs superlattices by going from a symmetric to an asymmetric distribution of the well and the barrier thickness within the unit cell of the superlattice. Reducing the barrier thickness dB to half the well thickness dW moves the lowest state in the conduction band from the X point in the AlAs barrier to the Γ point in the GaAs well. For dW=2dB, the band structure becomes therefore direct for all values of dW. This change in the type of energy gap is accompanied by a significant enhancement of the integrated photoluminescence intensity for asymmetric superlattices.

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