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MicroscopyInnovations 2017 Microscopy Today Innovation Awards

T e editors of Microscopy Today congratulate the winners of the eighth Microscopy Today Innovation Award competition. T e ten innovations described below advance microscopy in several areas: light microscopy, scanning probe microscopy, and electron microscopy. T ese innovations will make microscopy and microanalysis more powerful, more fl exible, more productive, and easier to accomplish.

Black-Silicon Induced-Junction Silicon Photodiode Aalto University, Finland

Developers: Mikko Juntunen, Juha Heinonen, Ville Vähänissi, Päivikki Repo, and Hele Savin

T is new photodiode eliminates the front surface refl ectance problem through a nanostructure created via inductively coupled plasma-reactive ion etching (ICP-RIE). T e resulting “black silicon” nanostructure exhibits feature sizes smaller than the wavelength of visible light. T e structure creates a

refraction index gradient, which causes essentially all incident photons to be absorbed, eliminating front surface refl ectance for a broad wavelength range (250–950 nm) and delivering 96% quantum effi ciency up to incident angles of 70°. T e nanostructure also diff racts light, increasing its optical path and increasing the response of these diodes in the near-infrared range. To eliminate recombination losses caused by implan- tation and dopants, a 20-nanometer-thick, negatively charged, alumina (Al 2 O 3 ) fi lm is deposited on top of the nanostructure. T e negative charge repels electrons and attracts holes, creating an inversion layer at the surface, resulting in an induced junction. T e induced junction causes no Auger recombination and no lattice damage, ensuring high collection effi ciency of low-wavelength photons absorbed close to the surface. T e wavelength regime around 250–300 nm has been a particular issue for commercial silicon photodiodes, and their quantum effi ciency has been limited to around 50% in this region. In contrast, this new photodiode surpasses even a 100% quantum effi ciency around 300 nm, as the excited electrons gain enough energy to ionize secondary electrons via impact ionization. Aside from better response, the new device exhibits perfor- mance similar to commercial photodiodes with respect to other fi gures of merit, like speed and linearity. T e manufacturing process for these diodes has fewer high-temperature steps than the typical commercial silicon photodiode process, which drives down production costs.


T ese new photodiodes are expected to be most useful where commercial diodes perform the worst: UV spectroscopy, UV light detection, and near-infrared broadband applications in low-light imaging. Additionally, these diodes should be important when sensing diff use light, as when detecting X-rays or gamma-rays with scintillators coupled to photodiodes. In such applications, the high-energy photon is absorbed by a scintillator material, which then in turn emits photons of visible wavelengths. Because a signifi cant fraction of the secondary photons exits the scintil- lator at a high angle, the improved performance of the new diode at high incident angles should be useful.

NanoScratch In-Situ Nanomechanical Testing in the SEM


Developers: Jason Oh, Syed Asif, Bartosz Nowakowski, Ryan Major, Sanjit Bhowmick, Eric Hintsala, Doug Crowson, Bernie Becker, and Edward Cyrankowski

T e Hysitron PI 88 is a depth- sensing nanomechanical test instrument designed for use inside scanning electron microscopes (SEMs). T is stage-mounted instrument provides quantitative micro- and nano-scale mechanical property measurements synchronized with SEM imaging. T e nanoScratch option for the PI 88 enables quantitative measurement

of both normal and lateral forces during in-situ nanomechanical tests, providing tribological information such as friction coeffi cient and delamination force. Reciprocating scratch tests can also be performed to study wear mechanisms over longer periods of time. Acquired data provide information concerning material behavior under simultaneous normal and lateral stresses, which may be supplemented by simultaneous high-resolution SEM imaging of the deformation process. Traditional in-situ nano- and micro-scale mechanical testing is conducted by applying stress and strain to a sample in the normal direction to obtain hardness and modulus through targeted nanoindentation testing or yield behavior through small-scale compression or tensile tests. However, the uniaxial nature of the tests makes it diffi cult to quantify material behavior under sliding conditions. With nanoScratch, in-situ

tribological tests are

accomplished by applying a normal load to the sample while also moving the sample laterally at a prescribed rate. During the test, force and displacement are measured between the probe and sample in both the normal and lateral directions using sensitive capacitive transducers. T e user-changeable probe is

doi: 10.1017/S1551929517000840 • 2017 September

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