High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings

Abstract

Micro-electronic devices often undergo significant self-heating when biased to their typical operating conditions. This paper describes a convenient optical micro-imaging technique which can be used to map and quantify such behavior. Europium thenoyltrifluoroacetonate (EuTFC) has a 612 nm luminescence line whose activation efficiency drops strongly with increasing temperature, due to T-dependent interactions between the Eu ion and the organic chelating compound. This material may be readily coated on to a sample surface by thermal sublimation in vacuum. When the coating is excited with ultraviolet light (337 nm) an optical micro-image of the 612 nm luminescent response can be converted directly into a map of the sample surface temperature. This technique offers spatial resolution limited only by the microscope optics (about 1 micron) and time resolution limited by the speed of the camera employed. It offers the additional advantages of only requiring comparatively simple and non-specialized equipment, and giving a quantitative probe of sample temperature.

Current Filamentation in LargeBi2Sr2CaCu2O8Benseman1, Koshelev2, Vlasko-Vlasov3 et al. 2015Phys. Rev. Applied260130View full textAdd to dashboardCite

“…For bath temperatures of 45 K and above, thermal imaging reveals self-heating over a broad area of comparable size to the mesa itself, with self-heating strongest in the center of the mesa. This is similar to the results reported in [14] and the results of numerical simulations of Bi-2212 mesa self-heating [6,7]. However, at bath temperatures of 35 K and below, a new type of behavior appears.…”

“…In this mounting scheme epoxies are avoided enabling optimal heat removal from the mesa. At bath temperatures of around 60 K and under correct biasing conditions, it can generate up to 60 μW of coherent far-field radiation at approximately 0.6 THz [14].…”

“…1a) has been employed for a number of applications in the past [27], while more recently we have used it for imaging self-heating in Bi-2212 mesas [14]. As described in [14] we take advantage of the temperature dependence of the 612 nm fluorescence line of the europium chelate compound europium thenoyltrifluoroacetonate (EuTFC). A recent variation of this technique employs a coating of SiC granules in place of the EuTFC film [15,16].…”

“…1a). We may thus estimate the mesa conductance with negligible self-heating as being the tangent to the I-V characteristic in this region (black lines on plot) as described in [14], allowing us to determine σ c (T) below T c , and convert our temperature maps into maps of the c-axis quasiparticle current density.…”

“…Also, if the pattern of self-heating is highly asymmetric with respect to the cavity mode being excited, then coupling of the Josephson oscillations to free space -and thus the level of emitted THz power -is predicted to be strongly enhanced [10]. Localized hot-spots have been observed in low-temperature scanning laser thermal microscopy (LTSLM) studies [11][12][13] as well as in thermoluminescence imaging [14][15][16]. Indeed, the highest levels of THz power observed to date from Bi-2212 mesa devices [17,18] occur in the presence of strong self-heating typical for hot-spot formation.…”