Understanding the Physics Understanding the Physics of Plasma Display of Plasma Display

AddressingAddressing

Vladimir NagornyVladimir Nagorny

(available at www.plasmadynamics.com)(available at www.plasmadynamics.com)

Addressing Speed and CostAddressing Speed and Cost

CostCost is the name of the is the name of the game todaygame today

Single-scanSingle-scan

Frame - 16.7Frame - 16.7msms ≥≥10 10 Subfields, ~1000 lines)Subfields, ~1000 lines)

Reset ~ Reset ~ 1.5-31.5-3msms

Sustain > 5-6ms, or it is Sustain > 5-6ms, or it is dimdim

Address ~ 7.7-10.2msAddress ~ 7.7-10.2ms

0.75-10.75-1s/line for single s/line for single scan HDTV addressingscan HDTV addressing

Three periods - three componentsThree periods - three components

Each period has its purpose, its specifics (priming, wall Each period has its purpose, its specifics (priming, wall charges), requirements (stability, efficiency, speed) and charges), requirements (stability, efficiency, speed) and problems.problems.

The purpose of the setup period is to place all cells into The purpose of the setup period is to place all cells into identical identical andand known known state. Usually it is in the corner of the Vt- state. Usually it is in the corner of the Vt-curve, where either PG or both PG and SG discharges are curve, where either PG or both PG and SG discharges are activeactive

The purpose of address period is to do the opposite -to The purpose of address period is to do the opposite -to discriminatediscriminate between ON and OFF cells, so that one can start between ON and OFF cells, so that one can start sustaining of the ON and not the OFF cellssustaining of the ON and not the OFF cells

The purpose of sustaining period are to produce The purpose of sustaining period are to produce picturepicture (light) and provide (light) and provide primingpriming

Starting point for addressingStarting point for addressing Assume that at the end of the reset Assume that at the end of the reset

period both SG and PG or at least PG period both SG and PG or at least PG discharges are active and ramp is stable. discharges are active and ramp is stable. Cell is in the corner of Vt-curve – Cell is in the corner of Vt-curve – breakdown boundary for 3 electrodes, breakdown boundary for 3 electrodes, which can be verified by measuring the which can be verified by measuring the Vt-curve. After that every cell is “locked”.Vt-curve. After that every cell is “locked”.

For addressing one unlocks line by line For addressing one unlocks line by line and addresses it. Unlocking the line for and addresses it. Unlocking the line for addressing brings every cell again in the addressing brings every cell again in the corner of the Vt-curve (or to the edge), corner of the Vt-curve (or to the edge), and extra voltage initiates the discharge.and extra voltage initiates the discharge.

Strong SG discharge transfers large Strong SG discharge transfers large charge between X and Y electrodes, charge between X and Y electrodes, which then assist sustaining. which then assist sustaining.

V AY

V XY

XY

AY

AX

XA

(sustain gapdischarge)

VA

VA

Reset Period

VbX

Y

Addressing vs. discharge “speed” Addressing vs. discharge “speed”

Addressing “speed” is the Addressing “speed” is the timetime T,T, required to required to reliablyreliably address the line – maximum address the line – maximum of individual discharges of individual discharges timestimes

- statistical delay- statistical delay

- formative delay- formative delay

- plasma decay time- plasma decay time

stat form decayT

stat

form

decay

VoltageCurrentDensity

statistical formative decay

Where statistical effects come Where statistical effects come from?from?

Electron density is zero, they present in the volume only Electron density is zero, they present in the volume only occasionally, so occasionally, so

1.1. when the voltage is applied there may be no electron in the when the voltage is applied there may be no electron in the volumevolume

2.2. when electron appear it may not start the discharge (#1) when electron appear it may not start the discharge (#1)

Sources of electrons Sources of electrons Metastables (Volume source ##1, 2) – not importantMetastables (Volume source ##1, 2) – not important

~10-15~10-15s s after strong discharge they can only produceafter strong discharge they can only produce 1 1 e/e/s s per cell, per cell,

much less after the ramp setup – not enough for addressingmuch less after the ramp setup – not enough for addressing

ExoemissionExoemission (Surface source #3 - best kind) - the only source (Surface source #3 - best kind) - the only source

capable of “working” for long time. Exoemission – almost capable of “working” for long time. Exoemission – almost

uniform above sustain electrodes, and absent elsewhereuniform above sustain electrodes, and absent elsewhere

V

1

2

3

Statistical effects (continue)Statistical effects (continue) When high voltage applied When high voltage applied

any electron starting from the any electron starting from the

wall (#3, #3’) will start the wall (#3, #3’) will start the

discharge discharge thethe only wayonly way to to

decrease statistical delay is to decrease statistical delay is to

increase exo-emission rate (by increase exo-emission rate (by

doping, …). doping, …).

Right?Right?

V

33'

Statistical effects (continue)Statistical effects (continue) When high voltage applied

any electron starting from the wall (#3, #3’) will start the discharge the only way to decrease statistical delay is to increase exo-emission rate (doping, …).

Right? WrongWrong

It’s It’s NOTNOT the only way the only way

(where the OTHER come (where the OTHER come from?)from?)

V

33'

Statistical effects – OTHER waysStatistical effects – OTHER ways Electrons diffuse and may end up Electrons diffuse and may end up

on the sidewalls. These losses on the sidewalls. These losses affect affect bothboth statistical and statistical and formative delays. The closer walls, formative delays. The closer walls, the more electrons (and ions) are the more electrons (and ions) are lost, more need to start discharge. lost, more need to start discharge. 3 and 3’ are not equivalent any 3 and 3’ are not equivalent any more more

stat stat ==statstat((stat 0stat 0, , LL11, L, L22, E, E) >>) >>stat0stat0

33'

V

Wall Wall

Statistical effects – OTHER waysStatistical effects – OTHER ways Electrons diffuse and may end up on Electrons diffuse and may end up on

the sidewalls. These losses affect the sidewalls. These losses affect bothboth statistical and formative statistical and formative delays. The closer walls, the more delays. The closer walls, the more electrons (and ions) are lost, more electrons (and ions) are lost, more need to start discharge. 3 and 3’ are need to start discharge. 3 and 3’ are not equivalent any morenot equivalent any more

stat stat ==statstat((stat 0stat 0, , LL11, L, L22, E, E) >>) >>stat0stat0

We can:We can: Move walls (Decrease losses)Move walls (Decrease losses) Increase Increase EE (Compensate losses (Compensate losses

by increasing by increasing e/ie/i production). production). EE -is the strongest factor -is the strongest factor

Concentrate source in the centerConcentrate source in the center All of itAll of it

33'

V

Wall Wall

V

33'

Wall Wall

Statistical effects – PDP cellStatistical effects – PDP cellPDP has physical walls (barrier ribs) PDP has physical walls (barrier ribs)

and virtual walls (shown). Both and virtual walls (shown). Both affect efficiency of exoelectrons to affect efficiency of exoelectrons to start the discharge start the discharge increase increase statistical delay (up to 10 times). statistical delay (up to 10 times). Also, as discharge initiated in zone Also, as discharge initiated in zone A feeds zones B and C it may A feeds zones B and C it may change the mode, as the region C is change the mode, as the region C is unstableunstable

Va=80V (3D PIC/MC)Va=80V (3D PIC/MC)

Emission from the edge does not Emission from the edge does not

produce self-sustaining discharge - produce self-sustaining discharge -

it decays. it decays.

Electron emitted in the center Electron emitted in the center

produced ~4.5 times stronger produced ~4.5 times stronger

avalanche than from the edge, and avalanche than from the edge, and

then number of particles increases then number of particles increases

with characteristic time ~ 43ns (this with characteristic time ~ 43ns (this

case) by itself.case) by itself.

Statistical effects – sliding Statistical effects – sliding dischargedischarge

In a strong electric field, electron diffusion across electric In a strong electric field, electron diffusion across electric

field may actually result in the avalanche sliding along the field may actually result in the avalanche sliding along the

surface. In a weaker field avalanche ends up close to the surface. In a weaker field avalanche ends up close to the

point of the point where electron trajectory crosses the point of the point where electron trajectory crosses the

surfacesurface

E

= 0

Statistical effects – PDP cell (cont.)Statistical effects – PDP cell (cont.)

Virtual walls can be moved away by Virtual walls can be moved away by

a)a) decreasingdecreasing potential of the potential of the

“left” (bus) electrode and“left” (bus) electrode and

b)b) Increasing the voltage across Increasing the voltage across

PG (between address and both PG (between address and both

sustain electrodes) – strong sustain electrodes) – strong

effect. effect.

HigherHigher EE (or(or VVaa) ) wider zone A wider zone A

of certain discharge initiation of certain discharge initiation

(if ionization is strong, it (if ionization is strong, it

overcompensates losses; even overcompensates losses; even

electron near the wall will start electron near the wall will start

the discharge)the discharge)

c) Decreasing aspect ratio PG/SGc) Decreasing aspect ratio PG/SG

Formative delayFormative delay Formative delay time is defined by the slowest - linear stage of the Formative delay time is defined by the slowest - linear stage of the

discharge. Both applied voltage and gap size strongly affectdischarge. Both applied voltage and gap size strongly affect formform

LL= = (e(eL L - 1) –1 - 1) –1 -- the most important parameter, it varies. the most important parameter, it varies. > 0> 0 discharge grows, discharge grows, < 0< 0 – decays; – decays; > 1 – > 1 – charge accumulates in the charge accumulates in the volume volume

Weak dischargeWeak discharge ( (<<1<<1)) Strong dischargeStrong discharge ( (>>1>>1), linear phase), linear phase

No field distortion, plasma Completely compensates No field distortion, plasma Completely compensates decays as fast as it growsdecays as fast as it grows field, plasma decays very slow field, plasma decays very slow

2( ) / ( / ) /brU U L U E p L

12

, ~ ~ iiform

Uv

L L

– – first and second Townsend coefficients,first and second Townsend coefficients,

UU – applied voltage, – applied voltage, LL – gap size, – gap size, EE – electric field, – electric field, pp – gas – gas

pressurepressure

Formative delay (3D cell)Formative delay (3D cell) formform is affected by wall losses (is affected by wall losses ( *, *, EE,..), just like,..), just like statstat same recipe (larger same recipe (larger EE, better configuration), better configuration)

Nonlinear (from Nonlinear (from ((jj)))) and related 3D effects and related 3D effects

( j )

j

The critical current at The critical current at

which which starts to increase starts to increase

depends on gap size depends on gap size

j~1/Lj~1/L22

VCurrent density

Vbr

The range of voltages with linearThe range of voltages with linear

behavior is wider for shorter gap,behavior is wider for shorter gap,

but discharge is much fasterbut discharge is much faster

Discharge development scenariosDischarge development scenariosSlow scenario Slow scenario (common)(common) – losses to – losses to

Y significantY significant

1)1) Both XA and XY grow as Both XA and XY grow as eett 2)2) XY reaches nonlinear stageXY reaches nonlinear stage3)3) Discharge transfers to XY; Discharge transfers to XY;

further development is further development is independent on independent on VVAA

Discharge development scenariosDischarge development scenariosSlow scenario Slow scenario (common)(common) – losses to – losses to

Y significantY significant

1)1) Both XA and XY grow as Both XA and XY grow as eett 2)2) XY reaches nonlinear stageXY reaches nonlinear stage3)3) Discharge transfers to XY; Discharge transfers to XY;

further development is further development is independent on independent on VVAA

Fast scenarioFast scenario – losses to Y low or – losses to Y low or suppressedsuppressed

1)1) XA grows as XA grows as ee’’tt,, ’>’>2)2) XA reaches nonlinear stage, XA reaches nonlinear stage,

strong XA dischargestrong XA discharge3)3) Field bifurcates and discharge Field bifurcates and discharge

switches to XA-Y; further switches to XA-Y; further development is independent on development is independent on VVAA

Discharge development scenariosDischarge development scenariosSlow scenario Slow scenario (common)(common) – losses to – losses to

Y significantY significant

1)1) Both XA and XY grow as Both XA and XY grow as eett 2)2) XY reaches nonlinear stageXY reaches nonlinear stage3)3) Discharge transfers to XY; Discharge transfers to XY;

further development is further development is independent on independent on VVAA

Fast scenarioFast scenario – losses to Y low or – losses to Y low or suppressedsuppressed

1)1) XA grows as XA grows as ee’’tt,, ’>’>2)2) XA reaches nonlinear stage, XA reaches nonlinear stage,

strong XA dischargestrong XA discharge3)3) Field bifurcates and discharge Field bifurcates and discharge

switches to XA-Y; further switches to XA-Y; further development is independent development is independent on on VVAA

One can suppress losses by decreasing Y potential, increasing A or One can suppress losses by decreasing Y potential, increasing A or choosing geometry, in which X and Y electrically not connected choosing geometry, in which X and Y electrically not connected SG>PG (Figure)SG>PG (Figure)

Plasma decayPlasma decay

Plasma decays primarily due to recombination:Plasma decays primarily due to recombination:

It is slow process, and there is not much one can do when It is slow process, and there is not much one can do when

the plasma density is high. However, this is not really a the plasma density is high. However, this is not really a

problem since the memory charge will then be determined problem since the memory charge will then be determined

by the final voltages of sustain electrodes, and ON and OFF by the final voltages of sustain electrodes, and ON and OFF

cell will still be significantly different. cell will still be significantly different.

*2

2

2

( , )

2

Xe Xe M Ne Xe Xe

e

M

XXe Xe e

Control knobs of the addressing speedControl knobs of the addressing speed

Exoemission rate – affects the statistical phase (priming)Exoemission rate – affects the statistical phase (priming)

Plate gap voltage (Plate gap voltage (VVAXAX) and size affect ) and size affect bothboth statistical and formative statistical and formative delays. Higher voltage and shorter plate gap (delays. Higher voltage and shorter plate gap (t ~Lt ~L-2-2) – better ) – better discharge timedischarge time

Configuration of electric field and voltage of the Y-electrode (Configuration of electric field and voltage of the Y-electrode (VVYY ) – ) – whether it suppresses or induce the electron transport to Y electrode whether it suppresses or induce the electron transport to Y electrode affects addressing. Stronger communication between X and Y affects addressing. Stronger communication between X and Y electrodes – worse addressing time electrodes – worse addressing time

One may increase the voltage One may increase the voltage VVAA, by applying unselectively , by applying unselectively VVOFFOFF to all to all cells of the line (between A and both X and Y), and using addressing cells of the line (between A and both X and Y), and using addressing drivers with only selected cells. If communication between X and Y is drivers with only selected cells. If communication between X and Y is suppressed, suppressed, VVOFFOFF and and VVAA may be quite large. may be quite large.

Depending on geometry, one may use additional voltage applied to Y Depending on geometry, one may use additional voltage applied to Y electrode, to either assist in formation the SG (XY) channel or electrode, to either assist in formation the SG (XY) channel or suppress XY communication (and premature XY discharge)suppress XY communication (and premature XY discharge)

Dual AddressingDual AddressingVVaddraddr=V=VON ON - V- VOFFOFF

In addition to VIn addition to VOFFOFF bias, one may bias, one may

decreasedecrease the voltage between the voltage between sustain electrodes (Vsustain electrodes (VXlockXlock) in ) in

order to better separate SG and order to better separate SG and PG discharges (PG discharges (obstructobstruct the the spread of the discharge across spread of the discharge across SG) and maximize VSG) and maximize VOFFOFF. .

V AY

V XY

XY

AY

AX

XA

V A

[Sakita, et al.]

[12]

Addressing: Short PG, no XY Addressing: Short PG, no XY communicationcommunication

1. End of the Ramp Setup1. End of the Ramp Setup 2. Address voltage (60V) is applied2. Address voltage (60V) is applied

3. After OFF discharge (V3. After OFF discharge (VOFFOFF=50V)=50V) 4. Beginning of the ON discharge4. Beginning of the ON discharge VVONON=60V, t=335ns=60V, t=335ns

Parameters of the Parameters of the OFF dischargeOFF discharge

Parameter /Va 30V 40V 50V 60V

Vgap, V 62 70 102 Break (ON)

, ns 270 155 118 xx

T(5000), ns 895 810 747 xx

Ni,max(105) 6.55 15 27.9 xx

Ttot, ns 770 680 472 xx

SummarySummary Understanding the mechanism of discharge development helps Understanding the mechanism of discharge development helps

to identify the nature of the problems and ways of solving them. to identify the nature of the problems and ways of solving them.

Most problems of address discharge are related to a low Most problems of address discharge are related to a low

exoemission rate and may be even more with exoemission rate and may be even more with inefficient inefficient

utilization of those electronsutilization of those electrons..

Using simple modifications of addressing scheme in order to a) Using simple modifications of addressing scheme in order to a)

increase addressing electric field by using two levels of increase addressing electric field by using two levels of

addressing voltage (addressing voltage (VVOFFOFF, V, VON ON = V= VOFF OFF + V+ VSS) and suppress ) and suppress

“communication” between regions (“communication” between regions (VVXlockXlock) and b) choosing ) and b) choosing

smaller the plate, gap can easily cut addressing time in half.smaller the plate, gap can easily cut addressing time in half.

Exoemission rate of 20-40e/Exoemission rate of 20-40e/s/cell and ther efficient use is s/cell and ther efficient use is

sufficient for addressing the line in about 0.5sufficient for addressing the line in about 0.5s s