“Plasmas Reactivos a Baja Temperatura. Caracterización y Diagnostico”. Isabel Tanarro Dept. de Física Molecular Inst. Estructura de la Materia (CSIC) Serrano 123. Madrid. Spain

CSIC, Madrid

3 Plasma “Materia gaseosa fuertemente ionizada, con igual número de cargas libres positivas y negativas”

Estado de la materia más abundante en el Universo. 99% en las estrellas y el espacio interestelar Emisión de Luz 4

LLightning Solar core Fusion reactor core Aurora Plasma Nebula Flame Laser focus Glow discharge Solids, Liquids & Gases Interplanetary space Solar corona Solar photosphere Jupiter core Si crystal Fusion plasma edge

CLASIFICACIÓN de los PLASMAS Grado de Ionización Plasmas débilmente ionizados ( N e / N < ) Plasmas con ionización media (10 -3 < N e / N < ) Plasmas fuertemente ionizados (10 -1 < N e / N) Temperatura Plasmas Calientes : T e  T N,T N+ Plasmas Fríos : T e >> T N,T N+ 6 cargas libres (N e ) partículas neutras (N) =

¿ DIFERENCIA PLASMA FRÍO - GAS IONIZADO ? Particle Energy (eV) Temperature (ºK) PLASMAS GASES Collective Effects N e, T e

+ Glow discharges: n e = cm -3, T e = 3 eV = K  D = 100  m D ( m ) = 50 √ T e / n e √  0 k / e 8 “Debye Length” (Shielding effect) Fundamental Magnitudes of Plasmas Plasma Dimensions >> Debye Length

Reflection vs. Transmission of EM Radiation   >  P dielectric (transparent)  <  P conductor (reflecting) “Plasma Frequeny” (resonance frequency for collective e - oscillations)  P ( Hz ) = 9 √ n e ( m -3 ) e / √ 4  0 m e D  P = √ kT e /m e  v e Metals : n e = m -3   Hz (UV) Fusion Reactor: n e = m -3   Hz (MW) Ionosfere : n e = 10 9 m -3   10 5 Hz (radio) 9 T e  K (3 eV)  v e = 10 6 m/s

Plasma Dimensions >> Debye Length Plasma Frequency >> Collision Frequency n e, T e 10 Plasmas Collective Behaviour !!! Electro-Magnetic Forces >> Dynamic Forces Gases Independent Particles Energy Transfer by Individual Collisions Gases vs. Plasmas

LLightning Solar core Fusion reactor core Aurora Plasma Nebula Flame Laser focus Glow discharge Solids, Liquids & Gases Interplanetar y space Solar corona Solar photosphere Jupiter core Si crystal Fusion plasma edge UV MW Radio 1 Å 10 nm 1  m 100  m 1 cm

LLightning Solar core Fusion reactor Aurora Plasma Nebula Flame Laser focus Glow discharge Solids, Liquids & Gases Interplanetary space Solar corona Solar photosphere Jupiter core Si crystal 1 cm 100  m 1  m 10 nm 1 Å

e-e- + _ Plasma production at Low Pressure in Electric Discharges Primary Ionization: [N e ] 0 (sea level)  10 3 cm -3 Electron Multiplication Secondary electron emission Paschen Curve

Other processes: Excitation of upper levels & de-excitation (light emission) Dissociation of Precursors & Production of New Species (Reactive Plasmas) Sputtering & Etching (Physical or Chemical)

T (eV) N (cm -3 ) ions in the glow electrons cathode ions stable species atoms & radicals etching products Far from Equilibrium!!! High T e  1 – 10 eV  10 4 – 10 5 K Low ionized plasmas (  10  6 )  Low energy transfer to the gas Low T GAS  eV  300 K Low Pressure, Glow Discharges (DC, RF, MW)