Through-membrane electron-beam lithography for ultrathin membrane applications

We present a technique to fabricate ultrathin (down to 20 nm) uniform electron transparent windows at dedicated locations in a SiN membrane for in situ transmission electron microscopy experiments. An electron-beam (e-beam) resist is spray-coated on the backside of the membrane in a KOH- etched cavity in silicon which is patterned using through-membrane electron-beam lithography. This is a controlled way to make transparent windows in membranes, whilst the topside of the membrane remains undamaged and retains its flatness. Our approach was optimized for MEMS-based heating chips but can be applied to any chip design. We show two different applications of this technique for (1) fabrication of a nanogap electrode by means of electromigration in thin free-standing metal films and (2) making low-noise graphene nanopore devices

Dynamical two-mode squeezing of thermal fluctuations in a cavity opto-mechanical system

We report the experimental observation of two-mode squeezing in the oscillation quadratures of a thermal micro-oscillator. This effect is obtained by parametric modulation of the optical spring in a cavity opto-mechanical system. In addition to stationary variance measurements, we describe the dynamic behavior in the regime of pulsed parametric excitation, showing enhanced squeezing effect surpassing the stationary 3dB limit. While the present experiment is in the classical regime, our technique can be exploited to produce entangled, macroscopic quantum opto-mechanical modes

Control of Recoil Losses in Nanomechanical SiN Membrane Resonators

In the context of a recoil damping analysis, we have designed and produced a membrane resonator equipped with a specific on-chip structure working as a "loss shield" for a circular membrane. In this device the vibrations of the membrane, with a quality factor of $10^7$, reach the limit set by the intrinsic dissipation in silicon nitride, for all the modes and regardless of the modal shape, also at low frequency. Guided by our theoretical model of the loss shield, we describe the design rationale of the device, which can be used as effective replacement of commercial membrane resonators in advanced optomechanical setups, also at cryogenic temperatures

Control of Recoil Losses in Nanomechanical SiN Membrane Resonators

In the context of a recoil damping analysis, we have designed and produced a membrane resonator equipped with a specific on-chip structure working as a "loss shield" for a circular membrane. In this device the vibrations of the membrane, with a quality factor of $10^7$, reach the limit set by the intrinsic dissipation in silicon nitride, for all the modes and regardless of the modal shape, also at low frequency. Guided by our theoretical model of the loss shield, we describe the design rationale of the device, which can be used as effective replacement of commercial membrane resonators in advanced optomechanical setups, also at cryogenic temperatures

Treatable childhood neuronopathy caused by mutations in riboflavin transporter RFVT2.

Childhood onset motor neuron diseases or neuronopathies are a clinically heterogeneous group of disorders. A particularly severe subgroup first described in 1894, and subsequently called Brown-Vialetto-Van Laere syndrome, is characterized by progressive pontobulbar palsy, sensorineural hearing loss and respiratory insufficiency. There has been no treatment for this progressive neurodegenerative disorder, which leads to respiratory failure and usually death during childhood. We recently reported the identification of SLC52A2, encoding riboflavin transporter RFVT2, as a new causative gene for Brown-Vialetto-Van Laere syndrome. We used both exome and Sanger sequencing to identify SLC52A2 mutations in patients presenting with cranial neuropathies and sensorimotor neuropathy with or without respiratory insufficiency. We undertook clinical, neurophysiological and biochemical characterization of patients with mutations in SLC52A2, functionally analysed the most prevalent mutations and initiated a regimen of high-dose oral riboflavin. We identified 18 patients from 13 families with compound heterozygous or homozygous mutations in SLC52A2. Affected individuals share a core phenotype of rapidly progressive axonal sensorimotor neuropathy (manifesting with sensory ataxia, severe weakness of the upper limbs and axial muscles with distinctly preserved strength of the lower limbs), hearing loss, optic atrophy and respiratory insufficiency. We demonstrate that SLC52A2 mutations cause reduced riboflavin uptake and reduced riboflavin transporter protein expression, and we report the response to high-dose oral riboflavin therapy in patients with SLC52A2 mutations, including significant and sustained clinical and biochemical improvements in two patients and preliminary clinical response data in 13 patients with associated biochemical improvements in 10 patients. The clinical and biochemical responses of this SLC52A2-specific cohort suggest that riboflavin supplementation can ameliorate the progression of this neurodegenerative condition, particularly when initiated soon after the onset of symptoms

Selective Coating Deposition on High-Q Single-Crystal Silicon Resonators for the Investigation of Thermal Noise Statistical Properties

none6Silicon resonators are widely used in a large class of applications including sensing and actuation, signal processing and energy harvesting. Very often, the application for which these sensors are designed requires the deposition of metallic thin films or other coatings, in order to modify the optical coupling, the electrical conductivity or other physical-chemical properties of the device, for actuation and detection purposes. Invariably, coatings degrade the quality factor (Q) of resonance by increasing the amount of energy dissipated during vibration. Generally, this is an unwanted effect. In fact, developing strategies for controlling damping due to film deposition is vital for the design of high-performance resonators requiring low energy losses. In this paper, we present the results of our strategy for damping control applied to a class of high-Q silicon resonators used for the investigation of thermal noise statistical properties in non- thermodynamic equilibrium both at room temperature and at cryogenic temperatures.E. Serra; M.Bonaldi; A. Borielli; L. Conti; G. Pandraud; P.M. SarroSerra, Enrico; Bonaldi, Michele; A., Borielli; L., Conti; G., Pandraud; P. M., Sarr

Low loss single-crystal silicon resonators for the investigation of thermal noise statistical properties

Silicon resonators are widely used in a large class of applications including sensing and actuation, signal processing and energy harvesting. Very often, the application for which these sensors are designed requires the deposition of thin films or coatings, in order to modify the optical coupling, the electrical conductivity or other physical-chemical properties of the device. Invariably coatings degrade the quality factor (Q) of resonance by increasing the amount of energy dissipated during vibration. Generally this is an unwanted effect. In fact, developing strategies for controlling damping due to film deposition is vital for the design of high-performance resonators requiring low energy losses. In this paper, we present the results of our strategy for damping control applied to a class of high-Q silicon resonators used for the investigation of thermal noise statistical properties in non-thermodynamic equilibrium both at room temperature and cryogenic temperatures

Developing high-optical quality silicon resonators working in the quantum regime

none10E. Serra; M. Bonaldi; A. Borielli; F. Marin; A. Pontin; L. Marconi; F. Marino; G.A. Prodi; G. Pandraud and; P.M. SarroE. Serra; M. Bonaldi; A. Borielli; F. Marin; A. Pontin; L. Marconi; F. Marino; G.A. Prodi; G. Pandraud and; P.M. Sarr