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OME 40-2-25-S, organic material effusion cell on DN40 (O.D. 2.75")
CF-flange with 2 cm³ quartz crucible and integrated shutter

• Patented design
• Thermal Conduction Cooling technique (TCC)
• Ideal for evaporation of organic materials
  and OLED applications
• Temperature range 15 - 350°C,
  optional below room temperature
• Fast and precise temperature control < ±0.02 K
• Crucibles capacities 2 cm³ and 10 cm³,
  16 cm³ and 35 cm³ on request
• UHV and MBE compatibility

The Organic Material Effusion Cell - OME - is the very latest effusion cell designed by Dr. Eberl MBE-Komponenten GmbH. Due to the new patented Thermal Conduction Cooling technique (TCC) the OME cell provides drastically improved operation conditions for low temperature evaporation of organic materials.

Conventional effusion cells with Thermal Radiation Cooling (TRC) show a poor cooling efficiency at low operation temperatures, due to the T⁴-dependency of the emitted radiation power according to the Stefan-Boltzmann-Law. This results in a low cell cooling rate making precise temperature control below 150°C very difficult.

Our OME cell uses the linearity of the heat transfer between a heated reservoir and a cooled heat sink to obtain a high cooling rate even at very low operation temperatures. Thus rapid cooling down, low thermal time constant and stable temperature control are achieved.
The new concept involves a liquid metal used as a thermal conductor that provides direct thermal connection between crucible and heat reservoir without isolating voids. This excellent thermal contact also guarantees a very uniform temperature distribution within the crucible.
Precise temperature measurement provided by a direct touching TC is a further advantage of the innovative OME cell design.

Schematic of Thermal Conduction Cooled OME cell

The diagram on the right compares the cooling rates of a typical TCC and a TRC cell versus operation temperature. The data of both diagramms were measured on a 2 cm³ OME cell.
The cooling rate of the TRC cell is increasing with cell temperature according to the Stefan-Boltzmann-Law while the cooling rate of the TCC cell is increasing linearly with temperature. Despite its larger thermal mass the cooling rate of the TCC cell is much higher at low temperatures and reaches 10°C/min even at 70°C cell temperature.

Cooling rates measured on TCC cell OME 40-Q2-S

TCC cell and TRC cell during cooling down procedure are compared in another diagram on the right. It shows the resulting temperature decrease of both cells starting at the same cell temperature of 150°C.
After switching off the cell heaters the TCC cell cools down about 4 times faster than a comparable TRC cell.

Temperatures measured on TCC cell OME 40-2-25-S

Application

The excellent low temperature properties of the TCC concept make the OME cell ideally suited for evaporation of temperature sensitive materials like organics or polymers.

In standard radiation-heated low temperature cells the evaporant may be locally overheated due to the direct view of the crucible onto the heater wires. In contrast the crucible of the OME cell never reaches temperatures higher than the actual temperature of the heat reservoir. Rapid heating up and cooling down rates avoid waste of expensive materials during non-operation times.

Temperature fluctation during long-time operation of an OME cell

On the left-hand side a diagramm shows the excellent long term temperature stability of the OME cell. The diagramm displays a test run at setpoint 100°C and a constant cooling water flow of 0.5 l/min.The measured stability during a period of 10h operation with PID controller is better than  ± 0.02 K.

OME 40-2-25 temperature characteristics at varied setpoints

The fast heating up and cooling down times of OME cells are shown on the second testing chart.
Remarkably cells with TCC technique allow heating up steps with absolutely no temperature overshoot, which prevents waste and potential destruction of the evaporant

OME 40-2-25 test run with variation of the cooling water flow

Operated with PID controller OME cells feature an unrivaled adjustment capability. The third diagramm demonstrates the fast compensation of varying cooling water flows. The deviation from setpoint never exceeds 0.2 K.
Nevertheless a constant cooling water flow > 0.5l/min is recommended.

Technical Data

Dimensions

Schematic drawing of the Organic Material Effusion Cell OME 40-2-25-S

Specific Data

For general information on CF mounting flanges see "Flange and Gasket Dimensions".

System manufacturer:    MBE-Komponenten, Omicron and other manufactures not separately listed
				[cm³]	[mm]		Option		[mm] / [mm]		[W] / [A]	Product Code	Product Code
		OME	40 -	2 -	25 -	S*, TS* -	E1, N2 -	Q -	LxxxD36		270 / 9	PS 30-10-C	Quartz 2-25
		OME	40 -	10 -	35 -	S*, TS* -	E1, N2 -	Q -	LxxxD36		270 / 9	PS 30-10-C	Quartz 10-35

 LAST UPDATE: MAY, 2006

© 2003 Dr. Eberl MBE-Komponenten GmbH