Scaling-induced enhancement of X-ray luminescence in CsI(Na) crystals

We report on the diameter dependence luminescence property of CsI(Na) crystals under X-ray excitation. When CsI(Na) crystal diameter decreases to nano-scale, the X-ray excited luminescence decay time is speeding up from ∼600 ns to ∼10 ns and 420 nm Na-related cathodeluminescence is affected drastically. The reason is confirmed that diameter reduction leads surface effect to accelerate the excitons' quenching. These measurement results identify a critical distinguished boundary ∼20 μm) of crystal diameter, which provide a new way to potential application of CsI(Na) crystals in the development of fast X-ray and gamma scintillator film detectors with large area.