Hi everyone, I need your valuable input and appreciate it in advance. I have synthesized SiC thin films on four different substrates (Zirconia, MgO, SiC and Si) by RF-magnetron sputtering. I did, steady state and time resolved photoluminescence study of these films. I found substrate dependent carrier life time i. e. highest at Si (6.52 ns) substrate and lowest on MgO (5.15 ns). Now I want to correlate the observed life time with the PL intensity of the SiC film grown on the different substrate. Can anyone tell me the exact physical parameters to correlate these two results (PL intensity and carrier life time)?. I am attaching the PL emission spectra of these films recorded at an excitation wavelength of 360 nm. In the attached file, 1-Zirconia, 2-MgO, 3-SiC and 4-Si represent the PL of SiC film on different substrates.
Hi Satyendra Kumar Mourya, I think the procedure may be more complex than that. The PL lifetime will give some indication but it is a multi stage process, Excitation conduction and recombination. It may be hard to rule out the possibility that you are simply changing one of these factors, rather than the effecting the actual carrier lifetime. PL lifetime as a function of temperature is also used to freeze out potential traps in the material. Certainly the PL intensity will be even more abstracted, as the interface of your material could simply be providing new trapping centers for freed electrons. I think the most conventional way is to try and measure the time resolved photo-conductivity, ie. Measure the resistance, and give the sample a pulse of light, then see how the resistance changes over time, and fades away after the light pulse.
Dear Kumar, you should consider the rate equations and the definition of quantum efficiency (QE) for the case of PL . Suppose you have a thin film whose constituents (molecules) are luminescent ( that is fluorescent), QE is defined as the ratio between the photons that the shined material releases and the number of absorbed incident photons shining on the sample \Phi=\frac{N_PL}{N_abs}. This ratio essentially depends on the competition between radiative and non-radiative processes. By working on a simple two states model, (see e.g. http://photobiology.info/Visser-Rolinski.html ) ground and excited, the decay rate of the excited state depends on the population of the excited state and on a decay constant k which is equal to the sum of the radiative constant k_r and the non-radiative constant k_nr. In the steady state condition this rate equals the rate of absorbed photons. The numer of PL photons per unit time are proportional to the radiative constant k_r and to the population of the excited state. This means that the QE=k_r/(k_r+k_nr) . Expressing the constants k in terms of lifetimes, being 1/tau=k_tot and 1/tau_r=k_r, the result is that QE=tau_nr/(tau_nr+tau_r).
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructures
- Thin Films