In-situ Detection of the High Pressure Metallic Phase In Silicon
Lei Dong, Jimmie A. Miller (UNCCharlotte, NC 28223) ,
John A. Patten (WMU)
2005 NSF DMII Grantees Conference, Scottsdale, Arizona
The goal is to detect in real time the high pressure phase as it happens. This experiment takes advantage of the optical transparency of silicon to infrared radiation. Signal change is detected when
metallic phase generated under high pressure. This metallic zone is presumed to be not transparent to the wavelength 1330nm IR, which coincide with our results: 10%~15% decrease voltage.
Tip
Wafer
A diamond tip(5um radius) is attached on
the end of the ferrule. IR light (1330nm
wavelength) radiates right through the diamond
tip.
Silicon wafer used in IR detection test
Silicon wafer (100), 4 inches diameter, 475~575 micrometer
thickness, one side polished
Infrared detecting diagram
There is a layer of gold vacuum deposited on the diamond tip before scratch starts.
After one or two scratching, there is an area of approximately 3~4 um in diameter
with gold removed. This area is the only spot on the tip that allows IR come
through.
Scatch and Stay Test (variables: laser driving current
and staying time period)
Scratching Parameters
250 mA driving current
Scratching speed: 0.305mm/sec (forward)
2.5mm/sec (backward)
500 mA driving current
200
Groove depth 150
measured on 100
50
AFM (nm)
0
A metallic phase area is generated under the pressure of the tool. As the
diamond tool going forward, metallic phase changes to amorphous phase.
SEM Image of scratch at 20mN load
250 mA driving current
180
Laser source: 1330nm,
beam size 10 micrometer, fiber coupled
120
30
Pressure at the tip: ~10-12GPa
1000 mA driving current
Laser driving
current (mA)
60
Loads: 20mN,30mN,40mN and 50mN
Formation of the metallic phase
SEM Image of Gold coating (2000 Angstroms thickness)
Staying time
(Sec)
Scratching Speed Test
2nd scratch
0 mN scratch
3rd scratch
2nd scratch
3rd scratch
0 mN scratch
1st scratch
2nd scratch
3rd scratch
0 mN scratch
2.9
3.4
1st scratch
2nd scratch
140
120
100
Groove Depth 80
60
(nm)
40
20
0
3rd scratch
3.2
2.8
2.6
2.4
2.2
2.7
2.5
2.3
500
1000
1500
2000
2500
stylus position (micrometer)
Scratch at load 20mN
3000
3500
2.8
2.6
2.4
2.2
2.1
0
3
detector voltage
(volt)
3
detector voltage (volt)
3.2
detector voltage (volt)
detector voltage (volt)
1st scratch
0
500
1000
1500
2000
stylus position ( micrometer)
Scratch at load 30mN
2500
3000
0
500
1000
1500
2000
2500
3000
3500
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2
1.9
0
500
1500
2000
2500
3000
3500
stylus position (micrometer)
stylus position (micrometer)
Scratch at load 40mN
1000
Scratch at load 50mN
Acknowledgement
The authors would like to thank NSF for funding this project . Jay Matthews from
Digital Optical Company provided great help and Scott Williams from UNCC Optical
Center lend me laser equipments for my experiments.
1000
scratching
speed
(mm/sec)
250
speed 3
1st scratch
Load 50 mN scratch
speed 2
0 mN scratch
Load 40 mN scratch
speed 1
Load 30mN scratch
Load 20 mN scratch
Speed1:
0.0002mm/sec
Speed 2: 0.002
mm/sec
Speed 3: 0.305
mm/sec
laser driving
current (mA)
This plot shows preliminary results about different scratching speeds from the laser-heating test.
There is a clear trend in this plot that the slower the speed, the more softening effect. Also, the
outputting power from the laser play its role. The higher the energy of the laser is, the deeper the
groove.