Ali Javey (Advisor)

Research Advised by Professor Ali Javey

BPN667: Optical Absorption Study of 2-Dimensional III-Vs

Hui Fang
Kuniharu Takei
2012

Recently, a new type of 2-D material, free standing InAs nanomembranes (thickness of 3 - 19 nm), as a representative of III-V semiconductors, was realized by layer transfer and this enables optical studies of 2-D InAs which were previously inaccessible, by decoupling those ultra-thin layers from original growth substrates to any optically transparent substrates. By using Fourier Transform Infrared (FTIR) spectroscopy, we directly observe the optical transitions from 2-D subbands, with energy spacing in line with the particle in the box model. Furthermore, it is found that the...

BPN533: Nanomaterial-Based Artificial Skin Sensor

Kuniharu Takei
Toshitake Takahashi
Chuan Wang
2012

Flexible large-scale devices are of great interest for wearable human interface applications. We have developed a technique of "uniform nanomaterial patterning" for the integration of high- performance inorganic nanomaterials on user-defined substrates. This project is to realize large scale flexible multi-functional electronics by utilizing nanomaterials such as nanowires, nanotubes, and nanoparticles. As one of applications, we here demonstrate mechanically flexible large scale high sensitive multi-functional artificial skin by proposing different types of sensors such as a...

BPN469: Ultra-Short Channel 1D-2D Compound Semiconductor on Insulator (XOI) FETs

Steven Chuang
Kuniharu Takei
2013

Recently, compound semiconductor on insulator(XOI)has risen as a promising platform for next generation high performance electronics, as it inherits advantages from both SOI and high mobility III-V materials. In order to test the performance limit of this platform, we plan on fabricating ultra-short channel XOI FETs. This project will involve various controlled experiments to better understand the underlying physics of XOI FETs, thus allowing us to progress towards the ultimate XOI FET.

Project end date: 08/16/13

BPN659: High Performance Flexible Integrated Circuits Using Carbon Nanotube Networks

Chuan Wang
Kuniharu Takei
Toshitake Takahashi
2013

In this Project, we report the use of high-purity semiconducting carbon nanotube networks and 2-dimensional III-V nanomembranes for high-performance integrated circuits on mechanically flexible substrates for digital, analog, and radio-frequency applications. We have demonstrated high-performance carbon nanotube thin-film transistors (TFTs) with on-current, transconductance, and field-effect mobility up to 15 uA/um, 4 uS/um, and 50 cm2/Vs. Using such devices, digital logic gates with superior bending stability have been demonstrated. We have also employed a self-aligned device...

BPN629: Large-Scale Carbon Nanotube Network Active Matrix Circuitry for Flexible and Stretchable Electronics

Toshitake Takahashi
Kuniharu Take
Chuan Wang
2013

In this project, we will explore a promising approach for large-scale flexible and stretchable electronics using semiconductor-enriched carbon nanotube (CNTs) solution. In conventional flexible devices, organic materials or amorphous silicon have been intensively explored, but its inherently low electrical performance limits the range of potential applications. Here, we use solution-based approach in which semiconductor-enriched CNTs (99 %) are deposited uniformly on wafer-scale flexible polyimide (PI) substrate or Polydimethylsiloxane (PDMS) substrate at room temperature, and obtain...

BPN686: Spatially Controlled Growth of III-V Semiconductors Toward Low-Cost and High-Efficiency PVs

Daisuke Kiriya
Maxwell Zheng
Rehan Kapadia
Zhibin Yu
2013

So far, extensive research has been carried out for III-V semiconductor materials from crystal growth to device fabrications. The reason for this is that III-V shows the highest energy conversion efficiency due to high absorption coefficient and optimal and direct band gap. However, there is problem for III-V applications, which is the high cost of raw materials. We are exploring a method which addresses this limitation. High optical quality crystals have been grown on selected tiny areas to make array of crystals such as on metal foils. This should be useful as a PV without any loss...

BPN634: Low Voltage and Fast Response Actuators

Zhibin Yu
2013

The conventional electrostatic actuators are operated at very high voltage relative slow response which prevents them from useful applications in providing mobility for making microrobots. There has been a lot of study on making electrostatic actuators based on polymers such as acrylic elastomers, HS3 silicone and silicon NuSil. All these materials need over one thousands volts to operate. We are going to make low operation voltage and fast response actuators using nanowire polymer composites. We are going to deposit polymer thin films on vertically aligned nanotube (nanowire) forest...

BPN625: Direct Growth of High Quality III-V Semiconductors on Metal Foils for Low-Cost, High-Efficiency PVs

Maxwell S. Zheng
Zhibin Yu
Rehan Kapadia
2013

The intrinsic advantages of III-V semiconductors for solar cells have been hobbled by the lack of low-cost substrates and processes, which has thus far limited market success of III-V solar cells. Here at Berkeley we are exploring a non-traditional approach which addresses these drawbacks. High optical quality polycrystalline InP films have been grown on non-epitaxial molybdenum substrates. Remarkably, these films with micron-sized grains have similar photoluminescence qualities as single- crystalline InP, and show great promise for high-efficiency, low-cost solar cells....

BPN750: Multi-Gas Detecting Chemical Sensor Platform

Hiroshi Shiraki
2014

Chemical sensitive field effect transistors (CS-FET), which are conventional MOSFETs without gate electrodes will be fabricated and applied for low energy consumption, highly sensitive, small size, multi-gas detecting chemical sensors. The work functions of transition metal oxides (TMOs) deposited onto the channels of the CS-FETs can be manipulated by the adsorption of chemicals onto their surfaces. These changes cause a change in the surface potential of the underlying Si channel, leading to the current modulation of the devices. By selecting appropriate TMOs, different chemicals...

BPN755: Carrier-Selective Oxide Contacts for Silicon Electronics

Corsin Battaglia
Xingtian Yin
Steven Chuang
Thomas Rembert
Hiroshi Shiraki
2014

Efficient carrier selective contacts are key to electronic devices based on silicon including sensors, microelectromechanical systems, field effect transistors and photovoltaics. We explore substoichiometric molybdenum trioxide (MoOx, x<3) as a dopant-free, hole-selective contact for silicon. As a proof of principle, we demonstrate a silicon solar cell with a MoOx hole contact delivering a high open-circuit voltage of 711 mV and a power conversion efficiency of 18.8%. Due to the wide band gap of MoOx, we observe a substantial gain in photocurrent of 1.9 mA/cm2 in the ultraviolet...