Matteo Lorenzoni | Istituto Italiano di Tecnologia / Italian Institute of Technology (original) (raw)

Papers by Matteo Lorenzoni

Applied Physics Letters, Dec 17, 2018

Cellulose, Mar 1, 2004

Periodate oxycellulose was subjected to alkaline hydrolysis at room temperature in both homogeneo... more Periodate oxycellulose was subjected to alkaline hydrolysis at room temperature in both homogeneous (cupriethylenediamine) and heterogeneous (sodium hydroxide) medium, and the degradation kinetics was followed for nearly three months. By comparing the obtained results with the degradation kinetics of both hydrocellulose and periodate oxycellulose reduced with tert-butylamine borane, it was demonstrated that the-alkoxy fragmentation of oxidised sites is a very fast reaction, which reaches completeness during the preparation of samples for viscometric analyses. The subsequent degradation is due to other mechanisms, such as autoxidation and peeling. A comparison between the degrees of polymerisation of periodate oxycellulose before and after its reduction allows the quantitative determination of dialdehyde groups, without the interference of reducing end groups. Although this technique might not be valid for other kinds of oxycellulose, it supplies a simple and fast method for the analysis of mildly oxidised cellulose. Abbreviations: TTC-2,3,5-triphenyltetrazolium chloride; DPv-viscosity-average degree of polymerisation; DPv ox-DPv of the oxidised samples; DPv oxred-DPv of the oxidised and reduced samples; CEDcupriethylenediamine; TBAB-tert-butylamine borane.

Resumen del trabajo presentado a la 10th Conferencia Fuerzas y Tunel, celebrada en Girona (Espana... more Resumen del trabajo presentado a la 10th Conferencia Fuerzas y Tunel, celebrada en Girona (Espana) del 5 al 7 de septiembre de 2016.

ACS Nano, May 3, 2021

Thermal silicon probes have demonstrated their potential to investigate the thermal properties of... more Thermal silicon probes have demonstrated their potential to investigate the thermal properties of various materials at high resolution. However, a thorough assessment of the achievable resolution is missing. Here, we present a probe-based thermal-imaging technique capable of providing sub-10 nm lateral resolution at a sub-10 ms pixel rate. We demonstrate the resolution by resolving microphase-separated PS-b-PMMA block copolymers that self-assemble in 11 to 19 nm half-period lamellar structures. We resolve an asymmetry in the heat flux signal at submolecular dimensions and assess the ratio of heat flux into both polymers in various geometries. These observations are quantitatively compared with coarse-grained molecular simulations of energy transport that reveal an enhancement of transport along the macromolecular backbone and a Kapitza resistance at the internal interfaces of the self-assembled structure. This comparison discloses a tip-sample contact radius of a ≈ 4 nm and identifies combinations of enhanced intramolecular transport and Kapitza resistance.

Applied Physics Letters, May 7, 2018

This paper presents mechanical actuation experiments performed on ultrathin suspended nanoscale s... more This paper presents mechanical actuation experiments performed on ultrathin suspended nanoscale silicon devices presenting Euler buckling. The devices are fabricated by a combination of focused ion beam (FIB) implantation and selective wet etching. By loading the center of curved nanobeams with an atomic force microscope (AFM) tip the beams can be switched from an up-buckled position to the opposite down-buckled configuration. It is possible to describe the entire snap-through process thanks to the presence of strong capillary forces that act as physical constraint between the tip and the device. The experiments conducted recall the same behavior of macro and microscale devices with similar geometry. Curved nanobeams present a bistable behavior, i.e. they are stable in both configurations, up or down-buckled. In addition to that, by the method presented, it is possible to observe the dynamic of a mechanical switch at the nanoscale. By artificially creating compressive buckling it is possible to turn planar structures, patterned with conventional micro/nano fabrication methods, into 3D structures with different shapes and mechanical properties. One of the most interesting property of micro/nanoelectromechanical systems (MEMS/NEMS) is the so called mechanically bistable mechanism. The simplest example is represented by a single beam, clamped on both sides, that buckles under axial compression; the resulting curved beam can switch between the two stable configurations. Using standard fabrication methods, microscale beams can be fabricated and artificially buckled thanks to the introduction of surface stress, producing the very same effect of an axial compression 1. Snap

Ultramicroscopy, Apr 1, 2018

The determination of nanomechanical properties is an intensive topic of study in several fields o... more The determination of nanomechanical properties is an intensive topic of study in several fields of nanophysics, from surface and materials science to biology. At the same time, amplitude modulation force microscopy is one of the most established techniques for nanoscale characterization. In this work, we combine these two topics and propose a method able to extract quantitative nanomechanical information from higher harmonic amplitude imaging in atomic force microscopy. With this method it is possible to discriminate between different materials in the stiffness range of 1-3 GPa, in our case thin films of PS-PMMA based block copolymers. We were able to obtain a critical lateral resolution of less than 20 nm and discriminate between materials with less than a 1 GPa difference in modulus. We show that within this stiffness range, reliable values of the Young Modulus can be obtained under usual imaging conditions and with standard dynamic AFM probes.

Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Aug 16, 2017

Nanotechnology, Jun 22, 2017

Unfortunately, we noticed a mistake in section 2.3 of this article. As it is stated in related pu... more Unfortunately, we noticed a mistake in section 2.3 of this article. As it is stated in related publications, the thermal scanning probe lithography presented here works with force pulses of 5 μs duration and not 5 ms. We are sorry for the inconvenience caused.

ACS Applied Materials & Interfaces, Nov 13, 2014

The creation of highly efficient guiding patterns for the directed self-assembly of block copolym... more The creation of highly efficient guiding patterns for the directed self-assembly of block copolymers by resistless nanolithography using atomic force microscopy (AFM) is demonstrated. It is shown that chemical patterns consisting of arrays of lines defined on a brush layer by AFM allow the alignment of the blocks of lamella-forming polymers. The main advantage of this method relies on the capability to create high-resolution (sub-10 nm line-width) guiding patterns and the reduction of the number of process steps compared to the state-of-the-art methods for creating guiding patterns by chemical surface modification. It is found that the guiding patterns induce the block alignment very efficiently, allowing the achievement of a density multiplication factor of 7 for block copolymers of 14 nm half-pitch, which is attributed to the combined effect of topographical and chemical modification.

Nanotechnology, Apr 4, 2017

Nanomaterials, Jan 4, 2020

We present and discuss the capability of grain boundaries to induce order in block copolymer thin... more We present and discuss the capability of grain boundaries to induce order in block copolymer thin films between horizontally and vertically assembled block copolymer grains. The system we use as a proof of principle is a thermally annealed 23.4 nm full-pitch lamellar Polystyrene-block-polymethylmetacrylate (PS-b-PMMA) di-block copolymer. In this paper, grain-boundary-induced alignment is achieved by the mechanical removal of the neutral brush layer via atomic force microscopy (AFM). The concept is also confirmed by a mask-less e-beam direct writing process. An elongated grain of vertically aligned lamellae is trapped between two grains of horizontally aligned lamellae. This configuration leads to the formation of 90 • twist grain boundaries. The features maintain their orientation on a characteristic length scale, which is described by the material's correlation length ξ. As a result of an energy minimization process, the block copolymer domains in the vertically aligned grain orient perpendicularly to the grain boundary. The energy-minimizing feature is the grain boundary itself. The width of the manipulated area (e.g., the horizontally aligned grain) does not represent a critical process parameter.

Applied Surface Science, Jun 1, 2018

Sub-30 nm patterning of molecular resists based on crosslinking through tip based oxidation,

Journal of vacuum science and technology, Nov 1, 2016

In this work, the authors employed Peak Force tapping and force spectroscopy to evaluate the stre... more In this work, the authors employed Peak Force tapping and force spectroscopy to evaluate the stress generated during the fabrication of doubly clamped, suspended silicon nanobeams with rectangular section. The silicon beams, released at the last step of fabrication, present a curved shape that suggests a bistable buckling behavior, typical for structures that retain a residual compressive stress. Both residual stress and Young's modulus were extracted from experimental data using two different methodologies: analysis of beam deflection profiles and tip-induced mechanical bending. The results from the two methods are compared, providing an insight into the possible limitations of both methods. V

Applied Physics Letters, Aug 17, 2015

Proceedings of SPIE, Oct 21, 2015

We present a continuous tip monitoring method during atomic force microscopy imaging based on the... more We present a continuous tip monitoring method during atomic force microscopy imaging based on the use of higher harmonics, which are generated in the repulsive regime as a result of the nonlinear interactions between the cantilever tip and the surface under study. We have applied this method to commercial rectangular microfabricated silicon cantilevers with force constants in the 45 N/m range and fundamental frequencies in the 300-400 kHz range and with tip radii below 10 nm. We have focused in the resonance of the 2nd flexural mode and the 6th harmonic using polystyrene surfaces. The simultaneous acquisition of topographic and higher harmonic images allows a continuous control of the state of the tip. The experimental results have been rationalized with computer simulations taking into account both the cantilever dynamics and the tip-surface interactions.

Beilstein Journal of Nanotechnology, Apr 19, 2017

We present a combined theoretical and experimental study of the dependence of resonant higher har... more We present a combined theoretical and experimental study of the dependence of resonant higher harmonics of rectangular cantilevers of an atomic force microscope (AFM) as a function of relevant parameters such as the cantilever force constant, tip radius and free oscillation amplitude as well as the stiffness of the sample's surface. The simulations reveal a universal functional dependence of the amplitude of the 6th harmonic (in resonance with the 2nd flexural mode) on these parameters, which can be expressed in terms of a gun-shaped function. This analytical expression can be regarded as a practical tool for extracting qualitative information from AFM measurements and it can be extended to any resonant harmonics. The experiments confirm the predicted dependence in the explored 3-45 N/m force constant range and 2-345 GPa sample's stiffness range. For force constants around 25 N/m, the amplitude of the 6th harmonic exhibits the largest sensitivity for ultrasharp tips (tip radius below 10 nm) and polymers (Young's modulus below 20 GPa).

Journal of Micro-nanolithography Mems and Moems, Sep 21, 2015

ABSTRACT We present a novel approach for the creation of guiding patterns to direct the self-asse... more ABSTRACT We present a novel approach for the creation of guiding patterns to direct the self-assembly of block copolymers. A neutral layer of a brush polymer is directly exposed by electrons, causing the cross-linking of the brush molecules, and thus changing its local affinity. The advantage relies on the achievable resolution and the reduction of the process steps in comparison with deep UV and conventional electron beam lithography, since it avoids the use of a resist. We envision that this method will be highly valuable for the investigation of novel high-chi DSA materials and complex guiding pattern designs, where pattern placement and resolution is becoming critical.

Conductive Atomic Force Microscopy