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AS4201 2011

Prof. Sebastian Lopez

AS4201 Otoño 2011

Clase 3

Prof. Sebastián LópezDepartamento de Astronomía

FCFM, U. De Chile

AS4201 2011


Caracterización de la cámara CCD del telescopioGOTO de Cerro Calán

Efecto fotoeléctrico Explicado por Einstein en 1905 (Nobel)

Fundamentos

AS4201 2011



Efecto fotoeléctrico

Fundamentos

AS4201 2011



No se puede explicar si la luz es una onda

Fundamentos

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AS4201 2011



Efecto fotoeléctrico

Fundamentos

AS4201 2011



Diferentes valores de la fun-ción de trabao

AS4201 2011


CCD: Charge Coupled Device

I n c r e a s i n g

e n e r g y

Valence Band

Conduction Band

1.26eV

p ! o t o n

Hole Electron

1 micrón

RAIN "#$%$N&!

B"C#E$% "'E&!

VER$ICA&C'NVE('RBE&$%**D *$+,N&!

H'RI)'N$A&C'NVE('R BE&$

&E'. E/'&%E !

*EA%"RIN+C(&IN,ER$+%"+% .,"''E !

Analogía

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E-osure /inis0ed uc3ets no4 contain samles o/ rain.

Con5eyor elt starts turning and trans/ers uc3ets. Rain collected on t0e 5ertical con5eyor is tied into uc3ets on t0e 0oriontal con5eyor.

Vertical con5eyor stos. Horiontal con5eyor starts u and tis eac0 uc3et in turn intot0e measuring cylinder .

7

A/ter eac0 uc3et 0as een measured t0e measuring cylinder is emtied ready /or t0e ne-t uc3et load.

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A ne4 set o/ emty uc3ets is set u on t0e 0oriontal con5eyor and t0e rocessis reeated.

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E5entually all t0e uc3ets 0a5e een measured t0e CC, 0as een read out.

%t t / CC, 1 %t t / CC, 2

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%tructure o/ a CC, 1.

$0e image area o/ t0e CC, is ositioned at t0e /ocal lane o/ t0e telescoe. An image t0en uilds u t0atconsists o/ a attern o/ electric c0arge. At t0e end o/ t0e e-osure t0is attern is t0en trans/erred i-el at atime y 4ay o/ t0e serial register to t0e on8c0i amli/ier. Electrical connections are made to t0e outside4orld 5ia a series o/ ond ads and t0in gold 4ires ositioned around t0e c0i eri0ery.

Connection ins

+old ond 4ires

Bond ads

%ilicon c0i

*etalceramic or lastic ac3ageImage area

%erial register

'n8c0i amli/ier


CC,s are are manu/actured on silicon 4a/ers using t0e same 0oto8lit0ogra0ic tec0ni9ues usedto manu/acture comuter c0is. %cienti/ic CC,s are 5ery ig only a /e4 can e /itted onto a 4a/er.$0is is one reason t0at t0ey are so costly.

$0e 0oto elo4 s0o4s a silicon 4a/er 4it0 t0ree large CC,s and assorted smaller de5ices. A CC, 0as een roduced y :0ilis t0at /ills an entire 6 inc0 4a/er; It is t0e 4orlds largest integrated circuit.

,on +room &BN&

%tructure o/ a CC, <.

'ne i-el

C0annel stos to de/ine t0e columns o/ t0e image

$ransarent0oriontal electrodesto de/ine t0e i-els5ertically. Alsoused to trans/er t0e

c0arge during readout

:lan Vie4

Cross section

$0e diagram s0o4s a small section a /e4 i-els! o/ t0e image area o/ a CC,. $0is attern is reaeated.

ElectrodeInsulating o-iden8tye silicon

8tye silicon

E5ery t0ird electrode is connected toget0er. Bus 4ires running do4n t0e edge o/ t0e c0i ma3e t0e

connection. $0e c0annel stos are /ormed /rom 0ig0 concentrations o/ Boron in t0e silicon.

%tructure o/ a CC, =.

'n8c0i amli/ier at end o/ t0e serialregister

Cross section o/ serial register

Image Area

%erial Register

'nce again e5ery t0ird electrode is in t0e serial register connected toget0er.

Belo4 t0e image area t0e area containing t0e 0oriontal electrodes! is t0e >%erial register? . $0is alsoconsists o/ a grou o/ small sur/ace electrodes. $0ere are t0ree electrodes /or e5ery column o/ t0e image area

%tructure o/ a CC, @ %tructure o/ a CC, 6

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%tructure o/ a CC, @.

$0e serial register is ent doule to mo5e t0e outut amli/ier a4ay /rom t0e edgeo/ t0e c0i. $0is use/ul i/ t0e CC, is to e used as art o/ a mosaic.$0e arro4sindicate 0o4 c0arge is trans/erred t0roug0 t0e de5ice.

E d g e

o /

% i l i c o n

160 m

Image Area

Serial Register

Read 'ut Amli/ier

B u s w i r e s

:0otomicrogra0 o/ a corner o/ an EEV CC,.


',

'%

R,R%

'utut Node

%ustrate

'utut $ransistor

Reset $ransistor

%ummingell

2µm'utut ,rain ',!

'utut %ource '%!

+ate o/ 'utut $ransistor

'utut Node

R

Reset ,rain R,!

%umming ell %!

&ast /e4 electrodes in %erial Register

%erial Register Electrodes

:0otomicrogra0 o/ t0e on8c0i amli/ier o/ a $e3troni- CC, and its circuit diagram.

Electric Field in a CC, 1.

$0e n8tye layer contains an e-cess o/ electrons t0at di//use into t0e 8layer. $0e 8layer contains ane-cess o/ 0oles t0at di//use into t0e n8layer. $0is structure is identical to t0at o/ a diode unction.$0e di//usion creates a c0arge imalance and induces an internal electric /ield. $0e electric otentialreac0es a ma-imum ust inside t0e n8layer and it is 0ere t0at any 0oto8generated electrons 4ill collect. All science CC,s 0a5e t0is unction structure 3no4n as a >Buried C0annel?. I t 0as t0e ad5antage o/3eeing t0e 0oto8electrons con/ined a4ay /rom t0e sur/ace o/ t0e CC, 40ere t0ey could ecome traed.It also reduces t0e amount o/ t0ermally generated noise dar3 current!.

n .

E l e c t r i c . o t e n t i a l

:otential along t0is line s0o4nin gra0 ao5e.


Cross section t0roug0 t0e t0ic3ness o/ t0e CC,

Electric Field in a CC, 2.

,uring integration o/ t0e image one o/ t0e electrodes in eac0 i-el is 0eld at a ositi5e otential. $0is/urt0er increases t0e otential in t0e silicon elo4 t0at electrode and it is 0ere t0at t0e 0otoelectrons areaccumulated. $0e neig0oring electrodes 4it0 t0eir lo4er otentials act as otential arriers t0at de/inet0e 5ertical oundaries o/ t0e i-el. $0e 0oriontal oundaries are de/ined y t0e c0annel stos.

n .


Region o/ ma-imumotential

C0arge Collection in a CC, C0arge $rans/er in a CC, 1

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p i x e l

b o u n d a r 1

C0arge ac3et8tye silicon

n8tye silicon

%i'2 Insulating layer

Electrode %tructure

p i x e l

b o u n d a r 1

i n c o 2 i n 3

p ! o t o n s

C0arge Collection in a CC,.

:0otons entering t0e CC, create electron80ole airs. $0e electrons are t0en attracted to4ardst0e most ositi5e otential in t0e de5ice 40ere t0ey create >c0arge ac3ets?. Eac0 ac3etcorresonds to one i-el

C0arge $rans/er in a CC, 1.

In t0e /ollo4ing /e4 slides t0e imlementation o/ t0e >con5eyor elts? as actual electronicstructures is e-lained.

$0e c0arge is mo5ed along t0ese con5eyor elts y modulating t0e 5oltages on t0e electrodesositioned on t0e sur/ace o/ t0e CC,. In t0e /ollo4ing illustrations electrodes colour coded redare 0eld at a ositi5e otential t0ose coloured lac3 are 0eld at a negati5e otential.

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$ime8slice s0o4n in diagram

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C0arge $rans/er in a CC, = C0arge $rans/er in a CC, @

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C0arge ac3et /rom suse9uent i-el enters/rom le/t as /irst i-el e-its to t0e rig0t.

C0arge $rans/er in a CC,

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