Fwd: Reminder: PhD Orals - Yuan Zhang, June 10, 2009, 9am, Packard 101

James W Conway toecutter4ranger at gmail.com
Tue Jun 9 23:21:26 PDT 2009

Not to be missed


Chase your Dreams...

Begin forwarded message:

> From: "Yuan Zhang" <zhangy at stanford.edu>
> Date: June 9, 2009 1:04:27 PM PDT
> To: "'H.-S. Philip Wong'" <hspwong at stanford.edu>, "'Arash  Hazeghi'"  
> <ahazeghi at stanford.edu>, "'Li-Wen  Chang'" <lwchang at stanford.edu>,  
> "'Saeroonter Oh'" <sroonter at stanford.edu>, "'SangBum Kim'" <kimsangb at stanford.edu 
> >, "'Deji Akinwande'" <dejia at stanford.edu>, <lanw at stanford.edu>, <ckenney at stanford.edu 
> >, "'Marissa Anne Caldwell'" <macaldwe at stanford.edu>, "'Jenny Hu'" <jennyhu at stanford.edu 
> >, "'Soogine Chong'" <sgchong at stanford.edu>, "'BI Lee'" <bilee at stanford.edu 
> >, "'Kerem Akarvardar'" <kerem at stanford.edu>, "'Xinyu Bao'" <xinyubao at stanford.edu 
> >, "'Dae Sung Lee'" <daesung at stanford.edu>, "'Jason Parker'" <jaypark at stanford.edu 
> >, "'Albert Lin'" <mrlin at stanford.edu>, "'Kyeongran Yoo'" <raneeyoo at stanford.edu 
> >, "'Cara Beasley'" <cbeasley at stanford.edu>, "'Jiale Liang'" <liangjl at stanford.edu 
> >, "'Xiangyu Chen'" <xiangyuc at stanford.edu>, "'Yi Wu'" <ywu1999 at stanford.edu 
> >, "'CHAI Yang'" <eeychai at ust.hk>, "'Nishant Patil'" <nppatil at stanford.edu 
> >, "'Kokab Baghbani Parizi'" <kokab at stanford.edu>, "'Kyooho Jung'" <kyooho at stanford.edu 
> >, "'Rakesh Gnana David Jeyasingh'" <jrgdavid at stanford.edu>, "'Duygu  
> Kuzum'" <duygu at stanford.edu>, "'Bipul C Paul'"  
> <bpaul at tari.toshiba.com>, <"Byoung-Jae Bae:"@stanford.edu>
> Cc: "'Lab'" <labmembers at snf.stanford.edu>, <cis-people at cis.stanford.edu 
> >
> Subject: Reminder: PhD Orals - Yuan Zhang, June 10, 2009, 9am,  
> Packard 101

> Nanoscale Phase Change Memory: Device Structure and Materials  
> Characterization
> PhD Oral Examination
> Speaker: Yuan Zhang, Department of Electrical Engineering, Stanford  
> University
> PhD Advisor: Prof. H.-S. Philip Wong
> Time: 9am (refreshments served at 8:45am)
> Date: Wednesday, June 10, 2009
> Location: Packard 101
> Abstract:
> Modern digital system requires the capability of storing and  
> retrieving large amounts of information at very high speed. Non- 
> volatile solid state memories retains information when the power is  
> turned off and is now the mainstream data storage device for many  
> applications including personal electronics such as iPOD, mobile  
> phones, and netbooks. The market for non-volatile memory (NVM)  
> technology has grown substantially in recent years. However, Flash  
> memory, the dominant NVM technology, is facing fundamental scaling  
> challenges. In view of this, research in various new memory  
> technologies have been explored and accelerated. Among these  
> exploratory memory technologies, phase change memory (PCM) is one of  
> the most promising candidates, given its simple structure, good  
> scalability, high speed, and long endurance.
> This talk consists of two parts.  In the first part, germanium  
> nanowire diode was implemented as selection device for PCM array.  
> Unidirectional programming and reading for PCM cell requires a  
> selection device in a memory array structure to enable large array  
> sizes. Having a diode selection device can not only reduce the read  
> disturbance and leakage power, but also have the potential to  
> further increase the array density, by three-dimensional stacking of  
> cross-point memory layers. Germanium nanowire pn junction diode is a  
> good candidate for selection device because it has good scalability,  
> requires low processing temperature and has high conductivity. We  
> demonstrated a phase change memory cell structure utilizing in-situ  
> doped crystalline germanium nanowire diode integrated with a phase  
> change memory cell. The vertical nanowire diode served as the bottom  
> electrode and the memory cell selection device. Electrical  
> measurement showed low reset current and rectifying programming  
> behavior. This method provides a possible path toward high-density,  
> 3D cross-point memory arrays.
> In the second part of the talk, we addressed the scalability for  
> both phase change materials and phase change memory devices. Phase  
> transition properties of commonly used phase change materials for  
> both thin blanket films and nanodot samples were studied using x-ray  
> diffraction, and size dependence of the phase change properties was  
> observed. We employed self-assembly diblock copolymer patterning to  
> fabricate sub-20nm phase change nanodots.  This diblock copolymer  
> patterning technique was additionally utilized to fabricate devices  
> with small contact areas to lower the reset programming current.  
> Reduced reset current was achieved compared to a conventional  
> structure. The device can be further scaled by patterning a single  
> self-assembled contact hole in each cell to demonstrate device  
> scalability below 20 nm.
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