Measurement and Evaluation of Local Surface Temperature Induced by Irradiation of Nanoscaled or Microscaled Electron Beams

Abstract

Electron beams (e-beams) have been applied as detecting probes and clean energy sources in many applications. In this work, we investigated several approaches for measurement and estimation of the range and distribution of local temperatures on a subject surface under irradiation of nano-microscale e-beams. We showed that a high-intensity e-beam with current density of 10^5-6 A/cm² could result in vaporization of solid Si and Au materials in seconds, with a local surface temperature higher than 3000 K. With a lower beam intensity to 10^3-4 A/cm², e-beams could introduce local surface temperature in the range of 1000-2000 K shortly, causing local melting in metallic nanowires and Cr, Pt, and Pd thin films, and phase transition in metallic Mg-B films. We demonstrated that thin film thermocouples on a freestanding Si₃N₄ window were capable of detecting peaked local surface temperatures up to 2000 K and stable, and temperatures in a lower range with a high precision. We discussed the distribution of surface temperatures under e-beams, thermal dissipation of thick substrate, and a small converting ratio from the high kinetic energy of e-beam to the surface heat. The results may offer some clues for novel applications of e-beams.

Keywords: Electron beam; Energy converting; Local temperature; Melting point; Nanoscale thermometry; Scanning electron microscopy; Thin film thermocouple; Transmission electron microscopy; Vaporization.

Fig. 1

TEM morphology images showing eight 1-nm holes drilled in a 60-nm-diameter single crystalline Si NW. This is done in 1–8 s, respectively, with a 0.5–1.0-nm-diameter HIEB of current 5 nA in a 200 kV TEM. a The original Si NW together with a 25-nm-diameter Au NW (appearing black in the image). b An image after eight nano-holes have been created by a HIEB. c, d Images of the same sample after in situ tilting for 10.0° and 20.0°, respectively

Fig. 2

Local melting effects observed in a SEM. a SEM image of a Pt-Cr TFTC array sample, showing two holes (highlighted with red arrows) were made by e-beam irradiation at the junction regions of two Pt-Cr TFTC sensors. b AFM image of the same two junctions, showing detailed 3D information of the two holes. c Four Pd-Cr TFTC sensors made on a 400-nm-thick, freestanding Si₃N₄ thin film window. Two TFTCs (highlighted with white arrows) at the left wide of the window were burnt with a focused 785 nm laser. d The corresponding output peak of the Pd-Cr TFTC when it was burnt with the laser

Fig. 3

SEM micrographs of [B(10 nm)/Mg(15 nm)]_N = 4 multilayers on SiC substrate annealed with HIEB in a SEM with the annealing currents of a 0 mA, b 9.9 mA, c 10.7 mA, and d 12.8 mA, respectively

Fig. 4

Images TFTC samples in Si and the testing results. a Optical image of a TFTC array on Si with junction size of 5.0 × 5.0 μm². b SEM image of the device center, showing 24 sensor junctions. c Measurement results of local temperature increment with the TFTCs under e-beam irradiation with different accelerating voltages and beam currents

Fig. 5

Distribution of local temperature under irradiation of a nanoscale e-beam. a A single crystalline Si NW with four nano-holes drilled with a HIEB in TEM. Two shallow holes are highlighted with blue arrows, and two through holes are highlighted with red arrows. b Estimated T(r) function for the local temperature versus distance to the central point

Fig. 6

A TFTC array and its measurement results. a SEM image of a Pt-Cr TFTC array sample on the front surface of a Si₃N₄/Si(100)/Si₃N₄ wafer. The TFTC array on the central of the device consisted of 24 TFTCs, which had junction size ranged from 2.0 × 2.5 to 8.0 × 8.5 μm². b Measured outputs from one TFTC sensor when a focused e-beam of diameter 1 micro was irradiating on a spot of the two metallic thin film stripes of the TFTC, namely Pt and Cr, at certain distance to the Pt-Cr junction region

Fig. 7

SEM images of a TFTC array and its measurement results. a SEM image of a Pt-Cr TFTC array on thick Si wafer with identical original junction size of 5.0 × 5.0 μm². One junction (highlighted with a dashed yellow frame) was cut with FIB to a junction area of 1.0 × 1.0 μm². b SEM image of the FIB fabricated junction area in (a). c Measured outputs from an original TFTC and the small junction TFTC under the same e-beam irradiation

Fig. 8

An illustration for the overall picture of the nominal local temperatures under irradiation of nano-/micro-scale e-beams. The gray oval indicates the comparison between small and large TFTCs on thick Si wafers. The yellow oval indicates the comparison between TFTCs on thick Si wafers and on freestanding Si₃N₄ thin film windows. For T > 1500 K, the data points are estimated values from morphology or phase change