Organolead halide perovskites (OHPs) have attracted extensive attention as light harvesting materials for solar cells recently, because of their high charge carrier mobility, high photoconversion effi ciencies, low cost, and simple methodology. Despite these advantages, the OHPs exhibit sweep-dependent hysteresis behavior in current-voltage characteristics fi lms, deteriorating the reliability of devices based on the OHPs. This study demonstrates reliable high on/off ratio ( I on / I off = 10 4 ) CH 3 NH 3 PbI 3 broadband photodetectors with buffer layer-free simple metal/semiconductor/metal lateral structure. At high external bias, poor on/off ratios and spikes in dark current and photocurrent are observed due to the migration of charged defect ions. The ion migration can be effectively inhibited at low external bias, and thus the devices show high I on / I off ratios and spike-free dark current and photocurrent. In addition, prevention of the prepoling in the CH 3 NH 3 PbI 3 fi lms by operating at the low external bias results in pronouncedly enhanced signal-to-noise ratios even under low intensity incident light. These results strongly propose that inhibiting the migration of charged defect ions in CH 3 NH 3 PbI 3 fi lms is a key in developing reliable high performance CH 3 NH 3 PbI 3 -based devices.

Efficiency of TiN diffusion barrier between Al and Si prepared by reactive evaporation and rapid thermal annealingThe properties of lOO-nm-thick Ti ss N 45 and Ti4sN55 films as diffusion barriers between silicon substrates and thin Cu films were studied by sheet resistance measurements, Rutherford backscattering spectrometry, Auger electron spectroscopy, secondary-ion mass spectrometry, transmission electron microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffractometry, and diode leakage current measurements. For unpatterned Siltitanium nitride/Cu samples, all the layers were intact and there was no indication of interdiffusion by conventional depth profiling techniques up to 700 ·C for Ti.;sN 45 and 900 ·C for Ti45N55 after 30 s rapid thermal anneal in N 2 , respectively. Leakage current measurements did not show deterioration of diode junction (with junction depth of 0.25 and 0.30 f..lm) up to 650°C for Ti ss N 45 and 800·C for Ti 4s N 55 . The improvement in failure temperature of the Nrich Ti4sN55 diffusion barrier is a result of the lower defect density and a more stable feature furnished by nitrogen stuffed at the defects. ' 5176

Tantalum (Ta) and tantalum nitride films (Ta2N and TaN) of about 50 nm thickness were reactively sputter deposited onto (100) Si substrate by using dc magnetron sputtering and their diffusion barrier properties in between Cu and Si were investigated by using sheet resistance measurement, x-ray diffraction, Auger electron spectroscopy, and Secco etching. With increasing amounts of nitrogen in the sputtering gas, the phases in the as-deposited film have been identified as a mixture of β-Ta and bcc-Ta, bcc-Ta, amorphous Ta2N, and crystalline fcc-TaN. Diffusion barrier tests indicate that there are two competing mechanisms for the barrier failure; one is the migration of Cu into the Si substrate and another is the interfacial reaction between the barrier layer and the Si substrate. For instance, we identified that elemental Ta barrier failure occurs initially by the diffusion of Cu into the Si substrate through the barrier layer at 500 °C. On the other hand, the Ta2N barrier fails at 700 °C by the interfacial reaction between Ta2N and Si substrate instead of the migration of Cu into the Si substrate. For the case of TaN, the barrier failure occurs by the migration of Cu into the Si substrate at 750 °C. It is also demonstrated that the diffusion barrier property is enhanced as the nitrogen concentration in the film is increased.

The properties of 100-nm-thick reactively sputter-deposited TiN films with different deposition conditions and one chemical-vapor-deposited film have been studied as diffusion barriers between Cu and Si by using sheet resistance measurements, x-ray diffractometry, etch-pit test, and Auger electron spectroscopy (AES). Based on Rutherford backscattering spectrometry (RBS), AES, and transmission electron microscopy (TEM) analyses, the relationship between the density, oxygen content, and microstructure of the as-deposited TiN film has been established. As the density of the TiN film decreases, the microstructure of the film becomes porous and the oxygen content in the film increases. The result of the etch-pit test has shown that the failure temperature of the TiN diffusion barrier varies from 500 to 750 °C, depending upon the microstructure of the film. It is concluded that high density of the TiN film is of primary importance in achieving a good diffusion barrier performance between Cu and Si.