Facilities & Services

The equipments and the methodologies developed in our labs for research purposes, are available also for external services. The Minima-lab team provides access to facilities, scientific consultancy or research expertise on a contract-basis to scientific institutions and private companies.
Hot Filament Chemical Vapor Deposition (HF-CVD) Apparatus
The apparatus consists of a stainless steel chamber equipped with instrumentation for the control and measurement of pressure and vacuum. A 4-channel mass flow meter allows one to control the composition of gaseous mixtures. The chamber is connected to a patented powder-flowing system formed by a powder reservoir, a gas inlet, a mixing chamber and a mass flow controller. The final Mo nozzle, which can be translated and rotated around its longitudinal axis, is designed to control delivery rates and the homogeneity of the powder distribution across the active area of the substrate. Joule-heated Ta filaments (T = 2200 °C) provide activation of the reactants. Substrate holders (made of Mo), are heated by AC current and kept in contact with Pt/Pt-Ir thermocouples.
Micro Wave Plasma Enhanced Chemical Vapor Deposition (PECVD) Apparatus
The core of the MW PECVD apparatus is a water-cooled stainless steel process chamber with a substrate holder of 70 mm diameter. The microwave system consists of a magnetron power generator (2.45 GHz, 500W) connected to a resonant tunable cavity through a circulator and a matching network. The substrate holder is a RF plate antenna connected to a RF power generator (13.56 MHz, 600W) through an automatically adjusted matching network. The process gases are introduced through three mass flow controllers in a quartz cylinder located in the cavity and connected to the process chamber. The process pressure ranges from 10-3 to 10 mbar. The MW PECVD equipment is controlled by LOOKOUT(TM) software, running on an external PC with an ethernet link.
Termal Chemical Vapor Deposition (T-CVD) Apparatus
The thermal chemical vapour deposition (CVD) system uses a flow reactor quartz tube (20 mm inner diameter, 25 mm outer diameter) inserted in a furnace (200 mm length). The reactor is kept under atmospheric pressure, within an operating temperature range of 200-1100 C. The apparatus is connected to a gas inlet and mass flow controller, and is equipped with a system for separate injection of gases, or liquids that are subsequently vaporized.
Field Emission Apparatus
The apparatus, designed and assembled in our labs, can be used in two differente anode-cathode configurations. For the analysis of planar cathodes, the anode is a hemispherical Mo probe ( diameter of 1.52 mm ). In the case of wire-like cathodes we use a planar Mo anode. The substrate holder can accommodate emitting samples with various geometries. The working pressure is in the range of 10-6 - 10-7 mbar. The anode can be translated toward the cathode by a linear precision actuator and moved in the (x,y) plane by two micrometrics knobs. The inter-electrode distance and the position in the (x,y) plane are controlled by a PC. The anode-cathode (A-K) distance is precisely evaluated by means of capacitance measurements. The emission current is measured by a Keithley 6485 picoammeter, with rms noise of about 1 pA. The measurement circuit is completed by a high voltage DC generator (8 kV) and a 100 MOhm protection resistance. The system allows us to vary the applied electric field during the measurement by sweeping the voltage at a fixed anode-cathode distance, or by changing the A-K distance at fixed applied voltage. Control of the whole system and data acquisition subsystems are governed by a purpose designed software implemented in Lab-VIEW.
Micro-Raman Spectrometer
Raman is a powerfull technique for the analysis of organic and/or inorganic mixed materials. It is often used to:
  • Identify organic molecules, polymers, biomolecules, and inorganic compounds both in the bulk and in individual particles,
  • Determine the presence of different carbon types (diamond, graphitic, amorphous carbon, diamond-like carbon, nanotubes, etc.) and their relative proportions, something for which it is particularly well suited
  • Determine inorganic oxides and their valence state
  • Measure the stress and crystalline structure in semiconductor and other materials.
Our Micro-Raman apparatus is composed of a multi-line horizontally-polarized c.w. Argon laser (maximum power: 100 mW ) , a triple-grating (300 - 600 - 1800 gr/mm) spectrometer (iHR550 - HORIBA JOBIN YVON) coupled with a liquid-nitrogen cooled CCD. The spectrometer is ideal for a variety of reserch application, including: Raman spectroscopy and pholuminescence spectroscopy (max resolution: 0.6 cm-1). The micro-stage allows one to reduce the investigated area to less than 1 µm of diameter. As an example we report in the following the Raman spectra of isolated multi-wall carbon nanotube (MWCNT) bundles (diameter: 5-20 nm )
Field Emission Scanning Electron Microscope (FE-SEM)
The Hitachi S-4000 Field Emission Scanning Electron Microscope is equipped with a cold cathode field-emission electron gun; emission extracting voltage ranges from 0 to 6,5kV, accelerating voltage from 0,5 to 1 kV (variable in 100 V step), 10 to 30 kV (variable in 1 kV step). The optical system is constituted of 2-stage electrostatic lenses: magnification ranges from 40 to 300000x.
Gas Sensing Apparatus
Resistive Sensor
The sensing element of this customized apparatus is a multifinger device, formed by interdigitated electrodes (Au, Au/Cr, Nb, NbN, Ag, Al with 20-40 μm spacing) patterned on SiO2/Si substrates. A back gate contact (patent) is prepared directly on the Si substrate, and the sensing platform is placed in a chamber equipped with flow-meters, vacuum/pressure meters, units for controlling the gate voltage, resistivity and heating. The automated control of the sensor state is facilitated by a computer interface, designed specifically for the management of working parameters and data acquisition, and a microcontroller is used for data elaboration and transmission by an appropriate communication protocol. Using this system, gas measurements can be performed from as low as 10 ppb, with a good degree of sensitivity. The system is able to read signals from many elements simultaneously (up to 13), which therefore enables the development of sensing platforms formed by arrays of different sensors within a single device.

Quartz Crystal Nano Balance (QCN)
The quartz crystal nano-balance (QCN) is a gas detection system that has been designed and constructed using engineering solutions that enable the probing of extremely low detection limits. The circuit oscillator comprises of a 4Mhz AT-cut quartz crystal, characterized by an almost zero frequency drift with respect to temperature, in the range 18-30°C. The quartz resonator, coated by the active sensing material, is sandwiched between a pair of electrodes and housed in a small sensor chamber (1cm3). The circuit has been assembled using a high quality Pierce oscillator that ensures very stable oscillations during measurements. Following gas adsorption the mass variations (Δm) of the layer are calculated via the Sauerbrey relation:

<Δf = - [(2f 2)/ ( A (ρ G))1/2)] Δm

An advantage of the QCN over alternative systems is that the high counter frequency allows for the monitoring of very small mass variations, with a sensitivity of a little as 4 nanograms/ Hertz. Complete and automated control of the gas flow system and the state of the sensor has also been realized, through the use of a computer interface with dedicate software for data acquisition and signal management. This control system assures the optimization of the sensor response, while also facilitating the controlled heating of the device.