Images 2013

First prize:

"Marigold of the nano world", Bikash Dev Choudhury, with contribution by Apurba Dev and Ahmad Abedin, Semiconductor Materials Group, ICT, KTH

A scanning electron microscope (SEM) image of Zinc oxide (ZnO) nanowire and Silicon (Si) micro pillar hierarchical structures. The image is recolored for aesthetical purpose and insets are the magnified and cross-section images of the structure. Colloidal lithography and plasma assisted dry etching processes are used to fabricate the Si pillars. ZnO nanowires are grown on the Si pillars by hydrothermal synthesis process. The hierarchical 3D structure has the advantage of large surface to volume ratio and refractive index modulation. Potential applications of such hierarchical structures include, antireflective coating (ARC), solar water splitting and H2 generation and for sensing.

Original image (jpg 533 kB)

 Second prize:

"Electromagnetic wind", Gleb Lobov, Optics and Photonics, ICT, KTH

Although a corona discharge phenomenon is known for many years, it is constantly being examined in new applications and novel principles. Cold plasma which forms around electrodes under a reasonably high voltage of the order of tens of kilovolts shows up in usual atmosphere as a bluish glow. Instead of a breakdown, charges are slowly dragged away from the discharge electrode (the needle) and fly toward the electrode of the opposite polarity (the collector). On their way they pass their kinetic energy to the gas molecules, creating the so called electrohydrodymanic wind. This effect was lately utilized in fluid dynamics, for instance to trap narcotic and viral particles straight from the breath out of a patient for a prompt lab-on-chip test (KTH MST group). Further on, flying ions settle on the collector electrode and, in case if it’s covered with a dielectric, form a static surface charge. This charge creates an electric field inside the dielectric which can attain the order of hundreds of volt per micron. This provides a possibility to use a unipolar corona discharge in so-called electrical poling of polymers, a procedure where breakdowns are strongly unwanted. If an electro-optical organic substance is used as a dielectric layer on the collector electrode, electric field will align molecules of the polymer, in other words the polymer will be poled. After such treatment the polymer can be used in electro-optical and photonic devices such as modulators, couplers, lasers and many others. Compared to known inorganic materials, which do not require poling, electrically poled polymers were reported to several times work faster and consume less power. These are the key features for further progress in telecommunication technology and photonic-to-chip integration.

 Honorable mentions

"Gold snowflakes", Jin Dai, Optics and Photonics, ICT, KTH

The image was taken with scanning-electron microscope. It shows the snowflake-shape patterns consisted of 20 nm diameter gold nanoparticles coated with 2nm silicon dioxide shell (Au@SiO2 NPs). The pattern was found on a NPs based light absorber, near the edge of the uniformly distributed Au@SiO2 NPs.

Original image (jpg 457 kB)

"Destroyed III-V nano holes and pillars", Fei Lou, with equal contribution by Himanshu Kataria, Semiconductor Materials, ICT, KTH

The sample was prepared with Electron Beam Lithography followed by Inductively Coupled Plasma etching. SiO2 film (red) was used as hard mask. During etching, InP/InGaAsP/InP nano holes and pillars (Blue) with aspect ratio around 10:1 were partly destroyed, forming the current morphologies. The hole radius and height are around 200 nm and 4 μm, respectively.

Orginal image (jpg 354 kB)

"Quantum well photoluminescence", Saulius Marcinkevicius, Optics and Photonics, ICT, KTH

Appearing like a flag, the image shows a near-field scan of the peak wavelength of InGaN quantum well photoluminescence.

Original image (pptx 412 kB)

"Microsphere sunset", Michael Fokine, Laser Physics, SCI, KTH

Image showing scattered light from a red HeNe laser beam impinging on the tip of an optical fiber during the fabrication of a microsphere. The fiber-tip is being heated by CO2-laser irradiation and can be seen to the right as bright light, indicating the wide spectrum of the black-body radiation. Part of the black body radiation is weekly guided downwards by the fiber. The HeNe laser is used as a visual guide for the infrared beam of the CO2 laser, operating at a wavelength of 10.6 µm. The photo is taken using a digital camera, without any post-manipulation. The scattered light is projected on white paper screen with the optical fiber, seen slightly out of focus, positioned between the laser/camera and the screen.

"ADOPT-day and -night on silicon membranes", Miao Zhang, with contribution by Torsten Schmidt, Material Physics, ICT, KTH

The image shows two free-standing, circular silicon membranes. The photographs were taken with an optical microscope, using bright field (left photograph) and dark field (right photograph) configuration. The two images are merged using Inkscape 0.48 and color enhancement was done with Paint Shop Pro 9.

The silicon membranes were fabricated by inductively coupled plasma (ICP) etching on a pre-patterned SOI wafer. The left image, the “sun”, depicts a 300 nm thick silicon membrane with a diameter of 512 µm. The color differences on the bright field image indicate a subtle change in membrane thickness due to diffraction of light on thin films. In contrast, on the dark field image only scattered light, collected by the objective lens, contributes. Thus, resulting in a dark background and features, which often stick up sharply from the smooth surface, appear bright. Moreover, since the silicon membrane is only 300 nm thick, it is transparent to the scattered light. Therefore, crap on the backside of the membrane can be also seen using dark field excitation. The “half-moon” is probably some cracked resist falling on the backside of the membrane.

Such silicon membranes with nanopores are currently fabricated and used in the NanoSilicon group in the frame of a SSF project aiming for parallel, optical DNA sequencing. Further applications can be, in conjunction with TEM analysis, size-correlated photoluminescence measurements on quantum dots deposited on such membranes or thinking of plasmonic studies even the deposition of gold nanostructures can be realized.
"Ferroelectric Jellyfish", by Michele Manzo, Quantum Electronics and Quantum Optics, SCI, KTH

Lithium Niobate is an artificial displacement ferroelectric crystal characterized by large pyroelectric, piezoelectric, acousto-optic, nonlinear and electro-optic coefficients features and is one of the key materials for the fabrication of integrated optical devices. By properly engineering the ferroelectric domains or the surface stoichiometry, via electric field poling as well as chemical surface modification (e.g. metal indiffusion, ion-exchange or etching), the crystal is also a perfect substrate for ferroelectric lithography and artificial photosynthesis.

The sample used is a selective proton-exchanged lithium niobate crystal which has been angular polished to investigate both the protons (H+) diffusion profile, and the impact of the proton-exchange on the crystal properties.

The image is the 2D spatial map of the phase signal obtained from piezoresponse force microscopy (PFM) measurements. The contrast is given by the orientation of the spontaneous polarization, which in lithium niobate can assume only two possible configurations, lying at 180º each other. In our sample, bright (dark) colors indicate the polarization is pointing onto (out of) the surface.

The body of the jellyfish is the proton-exchanged portion of the crystal. The quasi-parabolic shape matches the diffusion profile obtained when using a rectangular diffusion window. The fine spotted fractal decorations of the body of the jellyfish fade towards the inner core, and are mapping areas with different protons concentration and crystallographic arrangment. The tentacles are spontaneously switched ferreoelectric nanodomains (lateral size <200nm). As a consequence of a strong electrostic field arising at the interface between the proton-exchange and the bare crystal, several nanodomains are nucleated and propagate deeply into the substrate for several microns strictly following the crystallographic orientation. 

"Photoluminescence of Si quantum dots", Federico Pevere, with contribution by Ilya Sytjugov, Material Physics, ICT

This image, which is a composition of three different images of adjacent areas, shows the photoluminescence (PL) from Si quantum wells and quantum dots (QDs) fabricated from a silicon-on-insulator (SOI) sample (courtesy of Ilya Sytjugov). The acquisition was carried out with the PL setup of our research group (an inverted microscope, Zeiss Axio observer.Z1m, a spectrograph, Andor Shamrock 500i, and an EMCCD camera, Andor iXon3) by exciting the sample with a 405nm-wavelength laser. From the left to the right side of the image, each separate PL image was acquired by using a band-pass filter with a center wavelength of 600nm, 700nm and 753nm, respectively. The addition of false colors according to the corresponding wavelength and the overall composition (outer black frame included) were obtained by means of Adobe Photoshop CS6. Si QDs from SOI samples are very easy to fabricate and exhibit very narrow PL peaks, usually in the red region of the visible spectrum. This, together with their non-cytotoxicity, strengthens the possible future application of Si QDs as cheap and “green” single-wavelength emitters.

Original image (jpg 1.1 MB)

"Four seasons on Si nanocrystals", Anna Fucikova, Material Physics, ICT

Top-left: 6 nm passivated silicon nanocrystals (high concentrated spot with agglomerates of nanoparticles)

Top-right: 6 nm passivated silicon nanocrystals (spin-coated solution on silicon wafer, various thickness of polymers was formed)

Bottom-left: 5 nm dodecene passivated silicon nanocrystals ( high concentrated spot with agglomerates of nanoparticles)

Bottom-right: 3 nm hexane passivated silicon nanocrystals (high concentrated spot with crystallized impurities in the sample)

The images are taken by using Canon 550D camera connected directly to oculars of an optical inverted microscope (Zeiss Axio observer.Z1m) with an objective Nikon EC Epiplan Neofluar 10x / 0.70 NA. The The samples were observed in normal visible light. Different distance of the camera was chosen to enhance the artistic effect.

"CdSe nanocrystals under UV light", Mahtab Sangghaleh, Material Physics, ICT

The image shows the cross section view of silicon micro-pore arrays filled by CdSe nanocrystals under UV excitation (405 nm).

The samples are 4 μm pitch (center to center distance) and 2 μm wide pores fabricated by using ICP etching of silicon wafers. A droplet of 1 μl colloidal CdSe nanocrystals (2 nm diameter) with the diameter of 2 nm was put on the sample using a pipette. Under UV excitation only the filled pores emit blue light as it is expected for CdSe nanocrystals in the dimater range of 2 nm according to quantum confinement effect.

The image is taken by Zeiss camera connected to an inverted microscope using 100 x Nikon optical objectives. No color manipulation is done on the image. Siliocn micro-pore arrays are fabricated by Yashar Hormozan.

"The smallest Stockholm emblem?", Yiting Chen, Optics and Photonics, ICT, KTH

This is an original InLens-mode SEM image of a Stockholm emblem, which is fabricated by EBL(electronic beam lithography) with a about 400 nm thick layer of negative resist Ma-N 2403 on  silicon substrate, with the fingerprint of about 600 µm × 600 µm. Hopefully, it is maybe the smallest Stockholm emblem in the world. Actually, it’s totally realizable  to make a ten times smaller version of that pattern with positive resist.

Original image (jpg 466 kB)

Page responsible:Max Yan
Belongs to: School of Engineering Sciences (SCI)
Last changed: Oct 08, 2013