Role of Bi3+ ions for Er3+ ions efficient 1.54 μm light emission in Er/Bi codoped SiO2 thin film prepared by sol–gel method

Er/Bi codoped SiO2 thin films were prepared by sol–gel method and spin-on technology with subsequent annealing process. The bismuth silicate crystal phase appeared at low annealing temperature while vanished as annealing temperature exceeded 1000 °C, characterized by X-ray diffraction, and Rutherford backscattering measurements well explained the structure change of the films, which was due to the decrease of bismuth concentration. Fine structures of the Er3+-related 1.54 μm light emission (line width less than 7 nm) at room temperature was observed by photoluminescence (PL) measurement. The PL intensity at 1.54 μm reached maximum at 800 °C and decreased dramatically at 1000 °C. The PL dependent annealing temperature was studied and suggested a clear link with bismuth silicate phase. Excitation spectrum measurements further reveal the role of Bi3+ ions for Er3+ ions near infrared light emission. Through sol–gel method and thermal treatment, Bi3+ ions can provide a perfect environment for Er3+ ion light emission by forming Er–Bi–Si–O complex. Furthermore, energy transfer from Bi3+ ions to Er3+ ions is evidenced and found to be a more efficient way for Er3+ ions near infrared emission. This makes the Bi3+ ions doped material a promising application for future erbium-doped waveguide amplifier and infrared LED.