PZT and 3/20/80 PNZT from 5 K to Room Temperature ISAF 2014 Joe T. - - PowerPoint PPT Presentation

Radiant Technologies, Inc.

Electrical Properties of 20/80 PZT and 3/20/80 PNZT from 5 K to Room Temperature

ISAF 2014

Joe T. Evans Jr.

Radiant Technologies, Inc.

&

• Dr. David Daughton

Lake Shore Cryotronics, Inc.

Radiant Technologies, Inc.

Test Equipment

• Lake Shore Cryotronics and Radiant Technologies together

measured the electrical properties of 20/80 PZT and 3/20/80 PNbZT thin ferroelectric film capacitors from 5 K up to 300 K.

• The Vision data acquisition program executed automated tests of

single samples over a wide temperature range, commanding temperature changes using GPIB.

• Thermally-compensated electrical probe tips in the Lake Shore

cryogenic chamber maintained electrical contact with the sample

• ver the large temperature changes.

Radiant Technologies, Inc.

Lake Shore Cryogenic Chamber

Radiant Technologies, Inc.

Lake Shore Cryogenic Chamber

• The Lake Shore Cryotronics CRX-4K chamber has a hot chuck placed above a

cold finger.

• The cold finger first dropped to 5.0 K while the hot chuck maintained the

sample at room temperature.

• The hot chuck was then set to the first temperature of the test profile and

testing began.

Cold Finger Hot Chuck

Tester

• For temperature changes, the controller used a

ramp rate of 3K per minute and then soaked the sample at the new temperature for 10 minutes before starting tests.

Radiant Technologies, Inc.

Sample Descriptions

• Capacitor structure:
• Platinum top and bottom electrodes
• Glass passivation above the capacitor
• Chrome/Gold probe pads and traces
• Tested areas were 100µm2 & 40,000µm2.
• Thicknesses:
• 20/80 PZT = 2,600Å
• 3/20/80 PNbZT = 1,500Å

Radiant Technologies, Inc.

• 50
• 40
• 30
• 20
• 10

10 20 30 40 50

• 20
• 15
• 10
• 5

5 10 15 20

T y p e A B H y s te re s is fro m 1 0 K to 3 1 0 K

[ A B 4 0 3 , 1 0 0 u s ]

u C / c m 2 V o l ta g e

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

Hysteresis vs Temperature

40,000 µm2 20/80 PZT

Black = 10 K Red = 310 K

Radiant Technologies, Inc.

• 50
• 40
• 30
• 20
• 10

10 20 30 40 50

• 20
• 15
• 10
• 5

5 10 15 20

T y p e A B H y s te re s is fro m 1 0 K to 3 1 0 K

[ A B 4 0 3 , 1 0 0 u s ]

u C / c m 2 V o l ta g e

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

• H y s t 20V 100us +: P olar iz ation (µC /c m 2)

Hysteresis vs Temperature

40,000 µm2 20/80 PZT

Black = 10 K Red = 310 K 20 volts was necessary at 10 K for saturation but the 100 µs test period prevented breakdown of the at 20 volts at room temperature.

The test voltage vs temperature vs frequency envelope must be evaluated before starting long automated tests.

Radiant Technologies, Inc.

• 5 0
• 4 0
• 3 0
• 2 0
• 1 0

1 0 2 0 3 0 4 0 5 0

• 1 0
• 5

5 1 0

T y p e A D H y s te re s is v s T e m p e ra tu re 1 0 K to 2 5 0 K

[ O r a n g e, 1 0 0 u s ] u C / c m 2 Vo lta g e

• H y s t -12V 100us : P olariz ation (µC /c m2)

• H y s t -12V 100us : P olariz ation (µC /c m2)

• H y s t -12V 100us : P olariz ation (µC /c m2)

• H y s t -12V 100us : P olariz ation (µC /c m2)

• H y s t -12V 100us : P olariz ation (µC /c m2)

• H y s t -12V 100us : P olariz ation (µC /c m2)

• H y s t -12V 100us : P olariz ation (µC /c m2)

Hysteresis vs Temperature

40,000 µm2 3/20/80 PNZT

Black = 10 K Red = 250 K

Radiant Technologies, Inc.

10 20 30 40 50 60 70 1 2 3 4 5 6

Polarization Volts

Remanent Hysteresis

Remanent Hysteresis

Radiant Technologies, Inc.

Remanent Hysteresis

10 20 30 40 50 60 70 1 2 3 4 5 6

Polarization Volts

Remanent Hysteresis

Radiant Technologies, Inc.

Remanent Hysteresis Task

• 50
• 40
• 30
• 20
• 10

10 20 30 40 50

• 10
• 5

5 10 Polarization (µC/cm2) Voltage Unswitched - Logic 0 Switched - Logic 1 Remanent

Radiant Technologies, Inc.

Remanent Hysteresis vs Full Hysteresis

• 50
• 40
• 30
• 20
• 10

10 20 30 40 50

• 10
• 5

5 10 u C /c m 2 Voltage +Hyst 12V 100us: Polarization (µC/cm2): 5

Radiant Technologies, Inc.

Remanent Hysteresis vs Full Hysteresis

• 50
• 40
• 30
• 20
• 10

10 20 30 40 50

• 10
• 5

5 10 u C /c m 2 Voltage

• Hyst -12V 100us: Polarization (µC/cm2): 5

+Hyst 12V 100us: Polarization (µC/cm2): 5

Radiant Technologies, Inc.

Remanent Hysteresis vs Full Hysteresis

• 50
• 40
• 30
• 20
• 10

10 20 30 40 50

• 10
• 5

5 10 u C /c m 2 Voltage

Rhys t 12V 100us : Polarization (µC/c m 2): 5

• Hys t -12V 100us : Polarization (µC/c m 2): 5

+Hys t 12V 100us : Polarization (µC/c m 2): 5

Radiant Technologies, Inc.

• 40
• 30
• 20
• 10

10 20 30 40

• 20
• 15
• 10
• 5

5 10 15 20

Remanent Hysteresis 10k->310K

[ AB403, 100us ]

uC/cm2 Voltage

Remanent Hysteresis vs Temperature

40,000 µm2 20/80 PZT

• 20 volts with 100 microsecond period.

Blue = 10 K Red = 310 K

Radiant Technologies, Inc.

• 30
• 20
• 10

10 20 30

• 10
• 5

5 10

Type A D R em anent H ysteresis 10k->250K

[ AD403, 100us ] u C /c m 2 Voltage

Remanent Hysteresis vs Temperature

40,000 µm2 3/20/80 PNZT

• 12 volts with 100 microsecond period.

Blue = 10 K Red = 250 K

Radiant Technologies, Inc.

Coercive Voltage vs Temperature

40,000 µm2 3/20/80 PNZT vs 20/80 PNZT

• 6
• 4
• 2

2 4 6 50 100 150 200 250 300 350

Coercive Voltage  K

Coercive Voltage vs Temperature

20/80 PZT 3/20/80 PNZT

Radiant Technologies, Inc.

Remanent Polarization vs Temperature

40,000 µm2 3/20/80 PNZT vs 20/80 PNZT

5 10 15 20 25 30 35 40 45 100 200 300 400

Remanent Polarization  K

Remanent Polarization vs Temperature

20/80 PZT 3/20/80 PNZT

Radiant Technologies, Inc.

PUND

Drive Voltage Time Preset Pulse Delay Period

±Vmax

Positive Switched Pulse Positive Unswitched Pulse Negative Switched Pulse Negative Unswitched Pulse

Radiant Technologies, Inc.

PUND vs Frequency

100 µm2 20/80 PZT

20 30 40 50 60 70 80 90 100 110 120 0.0001 0.001 0.01 0.1 1 10 100 1000

µC/cm2 Log(ms)

PZT P* and P^ @ 250 K

• 9.9 volts from 1µs pulse width to 131ms pulse width.
• Definitions:

P* = switching pulse & P^ = non-switching pulse

Radiant Technologies, Inc.

Speed vs Temperature

40,000 µm2 3/20/80 PNZT

• 9.9 volts from 10µs pulse width to 131ms pulse width.
• Definitions:

P* = switching pulse & P^ = non-switching pulse

Radiant Technologies, Inc.

Speed vs Temperature

For both 20/80 PZT and 3/20/80 PNZT, when temperature increases the P* decreases while the P^ increases at a greater rate.

71 72 73 74 75 76 77 78 79 80 0.0001 0.001 0.01 0.1 1 10 100 1000

µC/cm2 Log(ms)

PNZT P* vs Temperature

40 K P* 70 K P* 100 K P* 130K P* 160 K P* 190 K P* 220 K P* 250 K P* 12 14 16 18 20 22 24 0.0001 0.001 0.01 0.1 1 10 100 1000

µC/cm2 Log(ms)

PNZT P^ vs Temperature

40 K P^ 70 K P^ 100 K P^ 130K P^ 160 K P^ 190 K P^ 220 K P^ 250 K P^

Radiant Technologies, Inc.

PUND vs Temperature

40,000 µm2 3/20/80 PNZT

• dP = P* - P^ = 2 x remanent polarization
• The remanent polarization decreases its magnitude with increasing temperature.
• The remanent polarization decreases in magnitude with decreasing pulse width.
• The switching speed vs pulse width slope remains constant down to 50 K.

Radiant Technologies, Inc.

deltaP vs Temperature

40,000 µm2 3/20/80 PNZT vs 20/80 PNZT

10 20 30 40 50 60 70 80 90 0.0001 0.01 1 100 C/cm2 Log(ms)

deltaP vs Temperature

20/80 PZT 3/20/80 PNZT

Cryogenic temperatures do not appear to affect ferroelectric switching speed.

Radiant Technologies, Inc.

Leakage vs Temperature

40,000 µm2 3/20/80 PNZT vs 20/80 PNZT

1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 100 200 300

µA/cm2 °K

Current Density vs Temperature at 1 volt

20/80 PZT 3/20/80 PZT

Radiant Technologies, Inc.

Dielectric Constant vs Temperature

40,000 µm2 3/20/80 PNZT vs 20/80 PNZT

50 100 150 200 250 300 350 400 450 500 50 100 150 200 250 300 350

Dielectric Constant  K

Dielectric Constant vs Temperature

20/80 PZT 3/20/80 PNZT

Radiant Technologies, Inc.

Conclusions

• It appears that tetragonal PZT does not have a phase

boundary from room temperature down to 5 K.

• Of the parameters of the hysteresis loop for both undoped

and niobium-doped PZT, only the coercive voltages change significantly with temperature.

• Switching speed for both compositions is unaffected by

temperature.

• Leakage decreases as temperatures decrease.

Radiant Technologies, Inc.

Conclusions

• Dielectric constant decreases as temperature decreases.
• Remanent polarization increases as the temperature

decreases.

– Switched polarization (P*) increases as temperature goes down. – Unswitched polarization (P^) decreases as temperature goes down.

20/80 PZT and its niobium-doped cousins appear to remain fully functional as memory devices down to 5 K.