Nanoscale Temperature Measurement Research Articles

Novel Nanocomposites for Luminescent Thermometry with Two Different Modalities.

In this work, we successfully integrated fluorescent nanodiamonds (FNDs) and lanthanide ion-doped upconversion nanoparticles (UCNPs) in a nanocomposite structure for simultaneous optical temperature sensing. The effective integration of FND and UCNP shells was confirmed by employing high-resolution TEM imaging, X-ray diffraction, and dual-excitation optical spectroscopy. Furthermore, the synthesized ND@UCNP nanocomposites were tested by making simultaneous optical temperature measurements, and the detected temperatures showed excellent agreement within their sensitivity limit. The simultaneous measurement of temperature using two different modalities having different sensing physics but with the same composite nanoparticles inside is expected to greatly improve the confidence of nanoscale temperature measurements. This should resolve some of the controversy surrounding nanoscale temperature measurements in biological applications.

Optical Thermometry with Quantum Emitters in Hexagonal Boron Nitride.

Nanoscale optical thermometry is a promising noncontact route for measuring local temperature with both high sensitivity and spatial resolution. In this work, we present a deterministic optical thermometry technique based on quantum emitters in nanoscale hexagonal boron nitride. We show that these nanothermometers show better performance than homologous, all-optical nanothermometers in both sensitivity and the range of working temperature. We demonstrate their effectiveness as nanothermometers by monitoring the local temperature at specific locations in a variety of custom-built microcircuits. This work opens new avenues for nanoscale temperature measurements and heat flow studies in miniaturized, integrated devices.

Nanoscale temperature measurement during temperature controlled in situ TEM using Al plasmon nanothermometry

Over recent years, the advent of microelectromechanical system (MEMS)-type microheaters has pushed the limits of temperature controlled in situ transmission electron microscopy (TEM). In particular, by enabling the observation of the structure of materials in their application environments, temperature controlled TEM provides unprecedented insights into the link between the properties of materials and their structure in real-world problems, a clear knowledge of which is necessary for rational development of functional materials with new or improved properties. While temperature is the key parameter in such experiments, accessing the precise temperature of the sample at the nanoscale during observations still remains challenging. In the present work, we have applied aluminium plasmon nanothermometry technique that monitors the temperature dependence of the volume plasmon of Al nanospheres using electron energy loss spectroscopy for in situ local temperature determination over MEMS-type microheaters. With access to local temperatures between room temperature to 550 ∘C, we have assessed the spatial and temporal stabilities of these microheaters when they operate at different setpoint temperatures both under vacuum and in the presence of a static H2 gas environment. Temperature comparisons performed under the two environments show discrepancies between local and setpoint temperatures.

Temperature dependence of secondary electron emission: A new route to nanoscale temperature measurement using scanning electron microscopy

Scanning electron microscopy (SEM) is ubiquitous for imaging but is not generally regarded as a tool for thermal measurements. Here, the temperature dependence of secondary electron (SE) emission from a sample's surface is investigated. Spatially uniform SEM images and the net charge flowing through a sample were recorded at different temperatures to quantify the temperature dependence of SE emission and electron absorption. The measurements also demonstrated charge conservation during thermal cycling by placing the sample inside a Faraday cup to capture the emitted SEs and back-scattered electrons from the sample. The temperature dependence of SE emission was measured for four semiconducting materials (Si, GaP, InP, and GaAs) with response coefficients found to be of magnitudes ∼100−1000 ppm/K. The detection limits for temperature changes were no more than ±8 °C for 60 s acquisition time.

Aluminum Nanoparticles as Fiducials for Nanoscale Temperature Measurements

Aluminum Nanoparticles as Fiducials for Nanoscale Temperature Measurements

Standard-based direct calibration method for scanning thermal microscopy nanoprobes

A direct calibration method, which is based on international temperature standards, developed for scanning thermal microscopy (SThM) nanoprobes is presented. The idea of calibration is intended mostly for use with thermoresistive SThM nanoprobes and is based on referencing the tip resistance to melting or freezing points of materials, which are contacted directly by the SThM tip. Particularly, in the presented experiment the gallium melting point is used, which is a defining fixed point of the International Temperature Scale of 1990 (ITS-90). Other points suitable for the SThM calibration are suggested, which makes the presented attempt the first step toward linking the quantitative SThM experiments with international temperature standards and therefore envisaging the traceability of nanoscale temperature measurements.

Numerical analysis of the temperature dependence of near-field polarization for nanoscale thermometry using a triple-tapered near-field optical fiber probe

A novel nanoscale temperature measurement method using near-field polarization, namely polarized near-field optics thermal nanoscopy (P-NOTN), has been developed. This method is performed in illumination–collection mode (I–C mode) using an Au-coated near-field fiber probe, and enables non-contact and nanoscale temperature measurement. The polarization change of the near-field light due to temperature change in the I–C mode is complicated. In order to confirm and understand the temperature dependence of the near-field polarization, and assess the validity of the temperature measurement by P-NOTN, numerical investigations were performed by the finite-difference time-domain (FDTD) method, which numerically solves Maxwell’s equations. Three-dimensional models of the Au-coated near-field fiber probe and the one-dimensional nanostructure as a sample (i.e. Au nanorod) were produced. The electromagnetic field between the probe tip and the nanoscale sample was calculated by the FDTD method in order to evaluate the polarization change in the I–C mode. The calculation results showed that the polarization plane in the near field changes as a function of the refractive index of the sample, which in turn is temperature-dependent. These calculation results verified the capability of P-NOTN to achieve nanoscale temperature measurement by detecting the temperature-dependent polarization rotation change in the near field.

High-Precision Nanoscale Temperature Sensing Using Single Defects in Diamond

Measuring local temperature with a spatial resolution on the order of a few nanometers has a wide range of applications in the semiconductor industry and in material and life sciences. For example, probing temperature on the nanoscale with high precision can potentially be used to detect small, local temperature changes like those caused by chemical reactions or biochemical processes. However, precise nanoscale temperature measurements have not been realized so far owing to the lack of adequate probes. Here we experimentally demonstrate a novel nanoscale temperature sensing technique based on optically detected electron spin resonance in single atomic defects in diamonds. These diamond sensor sizes range from a micrometer down to a few tens of nanometers. We achieve a temperature noise floor of 5 mK/Hz(1/2) for single defects in bulk sensors. Using doped nanodiamonds as sensors the temperature noise floor is 130 mK/Hz(1/2) and accuracies down to 1 mK for nanocrystal sizes and therefore length scales of a few tens of nanometers. This combination of precision and position resolution, combined with the outstanding sensor photostability, should allow the measurement of the heat produced by chemical interactions involving a few or single molecules even in heterogeneous environments like cells.

Near-field fluorescence thermometry using highly efficient triple-tapered near-field optical fiber probe

A novel local temperature measurement method using fluorescence near-field optics thermal nanoscopy (Fluor-NOTN) has been developed. Fluor-NOTN enables nanoscale temperature measurement in situ by detecting the temperature-dependent fluorescence lifetime of CdSe quantum dots (QDs). In this paper, we report a novel triple-tapered near-field optical fiber probe that can increase the temperature measurement sensitivity of Fluor-NOTN. The performance of the proposed probe was numerically evaluated by the finite difference time domain method. Due to improvements in both the throughput and collection efficiency of near-field light, the sensitivity of the proposed probe was 1.9 times greater than that of typical double-tapered probe. The proposed shape of the triple-tapered core was successfully fabricated utilizing a geometrical model. The detected signal intensity of dried layers of QDs was greater by more than two orders than that of auto-fluorescence from the fiber core. In addition, the near-field fluorescence lifetime of the QDs and its temperature dependence were successfully measured by the fabricated triple-tapered near-field optical fiber probe. These measurement results verified the capability of the proposed triple-tapered near-field optical fiber probe to improve the collection efficiency of near-field fluorescence.

A novel nano-scale non-contact temperature measurement technique for crystalline materials

A new high spatial resolution non-contact temperature measurement technique (thermal scanning electron microscopy, ThSEM) is demonstrated. It employs temperature dependent thermal diffuse scattering in electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). Unlike conventional scanning thermal microscopy, which uses contact probes, ThSEM is a non-contact method. In contrast to optical temperature mapping techniques, ThSEM does not have the spatial resolution limitation that arises from the optical wavelength and theoretically can reach a resolution of <10 nm. The hardware setup is very similar to the EBSD system in an SEM, which can make the integration of temperature mapping into an SEM relatively straightforward. Moreover, multiple signals or contrast mechanisms, such as temperature distributions, grain orientation maps, topographic images and elemental maps can be obtained from the same sample area depending on the specific SEM capability. This technique thus adds a new channel—the temperature signal—to the collection of existing SEM signals.

Quantification of electron–phonon scattering for determination of temperature variations at high spatial resolution in the transmission electron microscope

This work investigates the quantification of electron–phonon thermal diffuse scattering (TDS) for detection of temperature variations with nanometer spatial resolution in transmission electron microscopy (TEM). Observations of TDS intensity for (100) single crystal Si and Ge show interdependences of temperature and sample thickness which can be understood through the angular distributions of electron–phonon scattering as a function of temperature. The temperature sensitivity of the integrated TDS intensity can be of the order of 10−3 K−1 for Si and Ge. This shows that measurement of the TDS intensity in the TEM is a promising means for nanoscale temperature measurement; our measurements to date have demonstrated that temperature changes as small as 5 K are detectable.

Nanoscale thermal probing

Nanoscale novel devices have raised the demand for nanoscale thermal characterization that is critical for evaluating the device performance and durability. Achieving nanoscale spatial resolution and high accuracy in temperature measurement is very challenging due to the limitation of measurement pathways. In this review, we discuss four methodologies currently developed in nanoscale surface imaging and temperature measurement. To overcome the restriction of the conventional methods, the scanning thermal microscopy technique is widely used. From the perspective of measuring target, the optical feature size method can be applied by using either Raman or fluorescence thermometry. The near-field optical method that measures nanoscale temperature by focusing the optical field to a nano-sized region provides a non-contact and non-destructive way for nanoscale thermal probing. Although the resistance thermometry based on nano-sized thermal sensors is possible for nanoscale thermal probing, significant effort is still needed to reduce the size of the current sensors by using advanced fabrication techniques. At the same time, the development of nanoscale imaging techniques, such as fluorescence imaging, provides a great potential solution to resolve the nanoscale thermal probing problem.

M3-6 偏光した近接場光を用いたナノスケール温度・熱物性測定手法の開発(M3 熱流体デバイス)

Measurement of temperature distribution at nanoscale is absolutely important for the thermal design of high integrated devices. However, in conventional optical measurement techniques, the spatial resolution is limited by the diffraction limit of light, which is approximately half of the wavelength of the optical beam. Therefore, we have developed a novel optical nanoscale temperature measurement method using near-field microscope technique. We newly employed the polarization of light into the measurement principle, since the near-field polarization has a high sensitivity for the refraction index of the sample, which varies with temperature. In this method, highly polarization maintaining near-field optical fiber probe is necessary for increasing the measurement sensitivity. Hence, we have newly fabricated the single mode near-field optical fiber probe. In this paper, we report the verification of the new measurement principle and the comparison of the measurement sensitivity with the results using temperature dependence of reflectance.

Development of Nanoscale Temperature Measurement Technique Using Near-field Fluorescence

A nanoscale thermal system design, especially for the precise measurement of the temperature distribution in microfabricated devices using novel nanomaterials such as carbon nanotubes and fullerene has become increasingly important along with the development of nanotechnology. A new approach has been proposed toward an optical nanoscale temperature measurement method using near-field optics and fluorescence thermometry, namely, Fluor-NOTN (fluorescent near-field optics thermal nanoscopy). The topographic image and temperature dependence of a fluorescently modified sample, excited by near-field light, are simultaneously monitored. In this article, the temperature dependence of Cy3 fluorescent dye is verified near room temperature (298–308 K). A Cy3 mono-dispersed sample of a permalloy (Ni81Fe19) wire heater, 500 nm in width and 100 nm in thickness, is designed and fabricated. A localized temperature gradient of ΔT = 4 K within a submicron distance from the heater was successfully detected by near-field fluorescence with 100 nm spatial resolution.