Photoluminescence spectra of porous silicon modified by copper phthalocyanine coating
In this paper we present photoluminescence (PL) spectra of porous silicon (PSi) coated with thin top layer of copper phthalocyanine (CuPc). PSi was by electrochemical anodisation method prepared. CuPc based thin organic film was using physical vapor deposition (PVD) in high vacuum on the top of fresh PSi deposited. PL was under pulsed excitation measured and samples were in vacuum enclosed. PSi/CuPc samples exhibit strong photoluminescence in visible region at room temperature. Observed PL spectra exhibit multiband structure and such structure changes in red region compared to “clean” PSi. Properties of PSi/organic luminescence can be explained by penetration of organic material into PSi skeleton and interaction between carriers in PSi and deposited material.
Real-time multichannel scaler measurement of oscillator instabilities
This article describes measurement of oscillator instabilities by a method using the real-time multichannel scaler (RTMS). A theoretical model for such application is also considered. The general problem of the oscillator instability measurements in time domain is discussed. The results of oscillator instability measurements using the real-time multichannel scaler and a time interval analyzer are compared. The full range of application of this method is up to 7E-7 and depends strongly on the RTMS construction. We present the results of oscillator instability measurements of the order of 3E-5, using the RTMS with a resolution of 3.13 ns and the range of operation 3.28 ms.
Characterizing frequency stability: a continuous power-law model with discrete sampling
This paper examines several aspects of the Allan variance and the modified Allan variance. New expressions for these variances are derived for noise processes that produce power spectral densities with both integer and noninteger powers (/spl alpha/) in their functional dependence on f. A single expression, continuous over /spl alpha/, is presented for each of these variances. Also investigated are the effects of discrete sampling and finite data length. Discrete equations are developed and compared with more familiar continuous expressions. In addition, the uncertainty of the estimates for the Allan variance and the modified Allan variance for fully overlapping data usage is presented. The uncertainties can be calculated for arbitrary /spl alpha/. The results presented are compared with computer simulations and found to be in excellent agreement. >