Nickel‐related centers in HPHT microdiamonds for near‐infrared luminescent thermometry

Nano‐ and microcrystals of diamond are attractive for optical thermometry applications and possess unique optical properties as well as high chemical stability and biocompatibility. For biological application there are interest of diamonds with color centers that emit in the biological transparency window. One such defect is nickel‐related color centers that radiate in the near‐infrared range (1.4‐eV Ni centers), but have not yet been sufficiently investigated. This study reports the optical characteristics of HPHT diamond microcrystals with average sizes of 4 μm and 30 μm containing 1.4‐eV Ni centers. The temperature dependence of the spectral and temporal properties of Ni center emissions in the range from room temperature to 85 °C was demonstrated and thereby the possibility of appliance these centers as temperature sensors. The relative temperature sensitivities of luminescence peak intensity and lifetime for Ni centers were found to be 1.3% K⁻¹ and 0.42% K⁻¹, respectively. Moreover, the temperature determination accuracy reached better than 1 K.

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