Abstracts

May 15, 2013

MXene phases

Hossein Fashandi

MAX phases are a big family of ternary carbides (nitrides) with combined metallic ceramic properties. This family posses a graphite like planar atomic structure of metal carbides (nitrides), separated by a plane of a third element respectively depicted by MX and A. In 2011 a newly discovered 2d Material  was synthesized by selective removal of the A element from a MAX structure which due to the structural similarities to graphene was named MXene. Within a theoretical approach we carried out an extensive research on the electrical and structural properties of most of the potential MXene phases. The simulations are based on DFT approach using PBE and HSE06 psudopotentials using VASP package.  

A Printed Diode Operating at Ultra-High Frequency

Negar Sani

A printed rectifying diode manufactured on a flexible substrate, operating in the GHz range, is presented. We show that silicon and silicide in the form of powder with an average particle size of 1 μm can be used as the active layer of the diode. The production of the silicon and silicide powders is fairly simple as compared to the preparation route used for e.g. silicon nanoparticle ink. Except for the bottom electrode, which is made by photolithography of aluminum on PET foil, all layers of the diode, including the powders, are all printed. DC measurements show an average current capacity of 10 μA at 2 V forward bias, and a rectification factor of about 100 at 1 V. According to the measured frequency response of the diodes their cut off frequency is around 1.7 GHz. At 1.8 GHz, which is the frequency for the Global System for Mobile Communications (GSM), the diodes still have an output signal high enough to switch a printed organic electrochromic (EC) display. To demonstrate the use of this diode in power harvesting applications, a simple integrated circuit including an antenna, the diode and an EC display was printed on a flexible substrate. The antenna is designed to capture the signal of a mobile phone working in the GSM band. The signal transmitted from the mobile phone while making a call, is transferred to the diode through the antenna. The diode rectifies the signal and produces a DC voltage which is large enough to turn on the printed EC display. Under optimum conditions the display is switched in less than 10 s.

Construction of a new chemical vapor deposition system

Pontus Stenberg

A new hot wall chemical vapor deposition (CVD) system for silicon carbide (SiC) for semiconductor purposes is under design at IFM. The system is supposed to be able to use and mix between controlled amounts of 14 different gas sources and should be able to do both epilayer growth (~100 µm) as well as bulk growth of ~10 mm thick single crystals. This will be solved by doing several changes compared to the reactor designs used at IFM today; resistive heating instead of radio frequency (RF) heating and substrate pull for thick crystals are two examples of changed design.

Several subsystems have to be built and assembled for the CVD system. Growth chamber, gas system, heating system and control system are some sub systems used to divide the high complexity of the full system in to more graspable parts. Security is a main issue since the gases are poisonous, flammable and corrosive at the same time the growth part of growth chamber is hot (~1700 °C) with even hotter heating elements. The complete system is expected to cost ~8 million SEK. 

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Last updated: Sun May 12 12:19:36 CEST 2013