Thermal Stability Of Amorphous Ge-Sb-Se Films

Chalcogenide materials exhibit attractive optical properties such as large linear and nonlinear refractive index,broad transparency,and low phonon energy.Especially,the property of large nonlinear refractive index which makes them play an important role in optical applications that include all-optical switch,wavelength conversion,super continuous spectrum,and the light amplification.However,the flexible structure of chalcogenide glass is easy to relax due to the influence of temperature and light intensity,which will affect the stability of optical devices,and have great limitations on the application of chalcogenide optical devices.We here focused on a series of chalcogenide glasses from the Ge-Sb-Se system,with MCN ranging from 2.27 to 2.66.After annealing,the changes of optical and electrical properties caused by the changes of material structure of Ge-Sb-Se films with different components were studied.The relatively stable Ge-Sb-Se films were obtained.The main research works and results are listed as follows:1.The relationship between heat annealing time,film thickness and refractive index was studied.After annealing for different time(1h,3h,5h,15h,35h)at 20?below the glass transition temperature of each component of the film samples,the thickness of the films with MCN=2.27,2.33,2.4 decreased with the increase of annealing time,but the refractive index increased.While the thickness of the films with MCN=2.45,2.5,2.58 and 2.66 increased with the increase of annealing time,and the refractive index decreased.In addition,with the increase of annealing time,the film with MCN was 2.4 exhibited the smallest change ratio after long time(35 h)heat annealing in refractive index(<1%),and thickness(<3%).2.The transmission spectra of Ge-Sb-Se films before and after annealing were measured.It was found that the absorption edge of annealed Ge-Sb-Se films shifted blue(cut-off absorption edge moving to the short wave direction),and with the increase of annealing time from 0 h to 35 h,the blue shift of cut-off absorption edge became more and more obvious,at the same time,the optical band gap increased.When the MCN value of the films were close to 2.4,the change ratio of the films became small after long time(35 h)heat annealing in the optical band gap(<1%).3.The glass transition temperature T_gof the films was obtained by using resistance measurement system.The R-T test of the films was characterized at 10?below T_g.There's been a big change in the resistance for all films after heating for 1000s,in particular,the film resistance with MCN of 2.27 reduced by 97%.Compared with other component of the films,the film with MCN of 2.4 has the smallest change in resistance,which was 47%.4.The samples of Ge-Sb-Se film before and after annealing were further characterized by Raman laser.After annealing,Some changes had taken place in the SbSe_3/2triangle structure,GeSe_4/2structure,Se-Se bond,Sb-Sb bond and Ge-Ge bond,which led to changes in the refractive index of the films with MCN=2.27,2.33,2.45,2.50,2.55,2.60 and 2.66.However,there was no significant change in Raman spectra of the film with MCN=2.4 before and after annealing.In conclusion,through the optical and electrical characterization of the films after heat treatment,the film with MCN=2.4 has better thermal stability,which is more suitable for the thermal performance requirements of the device and has a higher refractive index,so it is an ideal optical material.