EPJ AP Highlight - Training for the first international nano-car race

A 3 step driving along the Au(111) track. The black cross indicates the tip position for the inelastic tunneling excitation of the Dresden molecule-vehicle.

The first international nano-car race will be held in Toulouse, France, during spring 2017, with the participation of six international teams. The training session of the Dresden Team is reported here.

To prepare their participation, Eisenhut et al. exercised on the Toulouse LT-UHV 4-STM reconfigured for the race with 4 independent controllers (one per scanning tunneling microscope (STM)). Their findings are reported in EPJ AP.


EPJ AP Highlight - Silicon Plasma Wave Receiver for Terahertz Wireless Communication

The signal to noise ratio (SNR) of the Si-CMOS receiver versus modulation frequency of the 300GHz carrier. The inset shows the block diagram with the main components: the patch antenna, the plasma wave FET, with schematically shown damped plasma oscillations, and the integrated wide-band amplifiers chain.

This paper presents the design, manufacturing and characterization of an integrated circuit (IC) that uses the plasma oscillations phenomena in silicon nanotransistors (Si-CMOS) for the detection of a 300 GHz-carrier-frequency wireless signal. We present the strategies for a Si-CMOS-based, wideband, integrated circuit receiver comprising: (i) a physics based, specific plasma-wave-transistor design, allowing impedance matching to the antenna and the amplifier, (ii) a patch antenna engineered through a stacked resonator approach and (iii) a broadband amplifier that uses bandwidth enhancement circuit techniques.


EPJ AP Highlight - Emergent gain materials for active photonics

Example of an optical waveguide containing colloidal quantum dots. When the nanostructures are optically pumped the waveguide propagates and confines the photoluminescence. Above a certain threshold light is amplified.

Nowadays semiconductor nanostructures developed by colloidal methods have emerged as an alternative to the classical III-V semiconductors and rare earth technologies to provide active functionalities in photonic devices. Their outstanding optical properties include high absorption cross section, high quantum yield of emission at room temperature, or the capability of tuning the band-gap with the size/base material. As a consequence, these materials have been successfully applied in several fields, such as photodetection, amplification, generation of light or sensing. For these purposes their solution process nature provides a cheap fabrication, and an easy incorporation on a broad range of substrates and photonic structures. This review summarizes the great effort undertaken by the scientific community to construct active photonic devices based on semiconductors fabricated by chemical methods. The works compares the performances demonstrated by semiconductor nanocrystals (colloidal quantum dots, quantum rods and quantum wells) with those provided by organometal halide perovskites, and describes their appropriate integration into photonic architectures (waveguides and cavities) to achieve stimulated emission.


EPJ AP Review - Imaging, single atom contact and single atom manipulations at low temperature

The LT-UHV-4-STM head and a 5.12 x 5.12 nm2 STM image of a letter C constructed atom by atom with 6 Au ad-atoms on Au(111) using here scanner PS3. I = 50 pA, V = 500 mV with ΔZ = 0.12 nm. Single atom manipulations tunnel resistance: 333 KΩ.

The new ScientaOmicron LT-UHV scanning tunneling microscope is installed at Pico-Lab CEMES-CNRS (Toulouse) with its 4 STM scanners performing on the same surface. At 4.3 K, we report state-of-the-art STM experiments on Au(111) usually performed on the most stable single tip LT-UHV scanning tunneling microscopes.

Operating the 4 scanners independently or in parallel with an inter tip apex distance lower than 100 nm, the ΔZ stability is better than 2 pm per STM. Single Au atom manipulations were performed on Au(111) recording the pulling, sliding or pushing signal. When contacting one Au ad-atom, a jump to contact leads to a perfect linear low voltage I-V characteristics with no averaging. Two tips surface conductance measurements were also performed with one lock-in and in a floating sample mode to capture the Au(111) surface states via two STM tips dI/dV characteristics. This new instrument is exactly 4 times as precise as a single tip LT-UHV STM.


EPJ AP Highlight - Slowing dynamics of a supersonic beam

2D imaging of the slowed Ar* supersonic beam for a final velocity vF = 61 m/s. From this image, one can easily extract the beam divergence and the coherence radius with respect to the position and size of the effective source.

The present investigation of the slowing dynamics of a supersonic atom beam by a counter-propagating resonant laser light, in other words the dynamics of atoms in a so-called “Zeeman slower”, is characterized by two special features which are: (i) a close coupling between simulations and experiments using a nozzle beam of metastable argon atoms, (ii) the use in the simulations of a Monte-Carlo (MC) scheme aimed at analysing step by step (i.e. subsequent cycles of absorption-emission) the slowing process and describing in a realistic way atom random walks due to the spontaneous emission. It allows us to get calculated 2D images and radial profiles of the slowed beam, in good agreement with experiment. Other important characteristics as angular aperture, velocity spreads, coherence radius (not easy to be measured experimentally), etc. also result from the simulation. Since the 3D atomic motion within the laser field is considered, border effects can be studied, while they were not directly accessible in a simple radiative force model. It is finally shown that the experimental characteristics of the slowed beam are reproduced by the calculated ones, assuming a point- like source. In general a laser beam is an efficient tool to manipulate the atomic motion and its interaction with atoms can be accurately characterized by means of the present MC-code. Actually any configuration combining resonant light and atoms is relevant (provided that the semi-classical approximation is valid), in particular the use of a “pushing” laser to generate a slow atomic beam from a magneto-optical trap is a technique which has been successfully tested with metastable argon atoms. Here again the MC-code has been able to accurately predict the characteristics of the generated beam.


New associate editors in EPJ AP

EPJ Applied Physics has appointed some new associate editors over the last two months and we are very pleased to introduce our new team and their expertise.

EPJAP now stands poised to continue its original goal to become an influential international journal. The recently appointed editors will contribute to its progress with new ideas and perspectives. They are all professional, outstanding scientist who have a vast experience and are strongly motivated towards excellence. We expect that the new editorial board will increase the benefits of the EPJAP's readers and authors even further in the future.


Virginie SERIN and Luis VINA new Co-Editors-in-Chief of EPJ Applied Physics

EPJAP is pleased to announce the appointment of Prof. Virginie Serin and Prof. Luis Viña as the journal’s new co-Editors-in-Chief. They will form an interdisciplinary leadership team for the journal.

Prof Virginie Serin and Prof Luis Viña’s terms begin on January 1, 2015. They are replacing Bernard Drévillon, who had served as Editor-in-Chief since the beginning of 2003. The new team will do its best to continue to build on the great work that their predecessor Bernard Drévillon has achieved during his term to further increase the global reach of the Journal, and to promote and encourage the recent progresses in the field of Applied Physics.


Structural, optical and nanomechanical properties of (111) oriented nanocrystalline ZnTe thin films

Structural, optical and nanomechanical properties of nanocrystalline Zinc Telluride (ZnTe) films of thickness upto 10 microns deposited at room temperature on borosilicate glass substrates are reported. X-ray diffraction patterns reveal that the films were preferentially oriented along the (1 1 1) direction. The maximum refractive index of the films was 2.74 at a wavelength of 2000 nm. The optical band gap showed strong thickness dependence. The average film hardness and Young's modulus obtained from load-displacement curves and analyzed by Oliver-Pharr method were 4 and 70 GPa respectively. Hardness of (1 1 1) oriented ZnTe thin films exhibited almost 5 times higher value than bulk. The studies show clearly that the hardness increases with decreasing indentation size, for indents between 30 and 300 nm in depth indicating the existence of indentation size effect. The coefficient of friction for these films as obtained from the nanoscratch test was ~0.4.

Structural, optical and nanomechanical properties of (111) oriented nanocrystalline ZnTe thin films, M.S.R.N. Kiran, S. Kshirsagar, M.G. Krishna and S.P. Tewari (2010), Eur. Phys. J. Appl. Phys. DOI 10.1051/epjap/2010071

Photoinduced Switching of Charge Carrier Mobility in Conjugated Polymers

In this paper we investigate theoretically a mode of heating thick layers using a laser beam where the temperature of the layer propagates in a steady-state self sustained fashion from the bottom of the layer towards the surface and may exhibit a very steep front. The propagation of the thermal front happens at a constant speed, related to the intensity of the power flux. To achieve this heating mode the absorption coefficient of the layer has to remain low in weak temperatures and increase rapidly as a function of temperature in higher temperatures. Additionally, a significant temperature increase must be generated to trigger this propagation mode, for example through the presence of a strongly absorbing layer beneath the transparent layer. The mode is well suited to semiconductors, especially silicon . The theoretical approach is confirmed by a simulation in the case of a low doped silicon layer 150 micrometers thick above a highly doped substrate ; the low doped silicon is heated homogeneously at 1476 K by a 2E6Wcm-2 CO2 laser beam throughought the entire thickness in a timescale of 20µS.

Photoinduced Switching of Charge Carrier Mobility in Conjugated Polymers, M. Weiter, J. Navrátil, M. Vala and P. Toman (2009), Eur. Phys. J. Appl. Phys. DOI 10.1051/epjap/2009112

Evaluation of organic sub-monolayers by X-ray based measurements under gracing incident conditions

The structural investigations of model organic systems like pentacene in the monolayer regime is very important for fundamental understanding of the initial nucleation process together with the electronic performance of transistor devices. The fact that the transistor performance saturates after deposition of some monolayers of the active organic material motivates a basic investigation of the submonolayer and monolayer regime in more detail. In this paper a method for the evaluation of the island formation and the island growth within the first monolayer is introduced. The method is based on X-ray scattering under grazing incident condition by means of specular X-ray reflectivity and off-specular X-ray scattering. From the specular reflectivity the electron density can be obtained which is directly correlated with the coverage of a submonolayer. Within the presented experiment coverages ranging from 7% up to 97% could be identified and are in excellent agreement with atomic force microscope results. Lateral information on the islands is obtained by rocking curve and detector scan measurements under grazing incident condition. The observed correlation peaks are evaluated by using Distorted Wave Born approximation, whereby mean island sizes ranging from 300nm to 1.5µm and mean island separation of about 2µm could be determined for the various samples. The obtained results encourages the use of this type of investigation for in-situ growth experiments to obtain a better understanding of the first monolayer formation.

Evaluation of organic sub-monolayers by X-ray based measurements under gracing incident conditions, O. Werzer, B. Satdlober, A. Haase, H.-G. Flesch and R. Resel (2009), Eur. Phys. J. Appl. Phys., DOI 10.1051/epjap/2009038