[labnetwork] [EXT] Black Layer Formation During Au E-Beam Evaporation

[Phyllis R. Nelson]

Hi Chandan,

"Black gold" coatings have been used for IR absorption for many years. Perhaps you are creating conditions for its formation?

Here is a reference: Deposition and characterization of far-infrared absorbing gold black films, https://opg.optica.org/ao/abstract.cfm?uri=ao-32-7-1136

Phyllis R. Nelson, PhD
Professor, Electrical and Computer Engineering
Director, Center for Exploration and Space Technologies
California State Polytechnic University, Pomona

email: prnelson at cpp dot edu

office: 9-317
phone: (909) 869-2649 (email preferred)

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I found it!) but 'That's funny ...' - Isaac Asimov

________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Chandan H B <chandanachar95 at gmail.com>
Sent: Thursday, September 17, 2026 2:21 AM
To: labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: [EXT] [labnetwork] Black Layer Formation During Au E-Beam Evaporation

You don't often get email from chandanachar95 at gmail.com. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification>
CAUTION: External Email, see notice below



Dear LabNetwork Community,

We would like to seek inputs from cleanroom/fab facility managers and process owners regarding an issue observed during Au deposition in our E-Beam Evaporators.

We have observed the formation of black/dark layer on the Au charge after a few melt cycles. The observation occurs during repeated melting of Au in a tungsten liner/crucible. We are currently investigating whether this could be related to material surface contamination, crucible/liner condition, outgassing, chamber history, or the Au pre-cleaning/conditioning procedure.

We would appreciate your experience on the following:

  *   Have you observed black/dark spots or a black layer forming on Au during repeated E-beam melting/evaporation?
  *   What Au purity and material form do you use?
  *   Do you perform any cleaning/degreasing of the Au charge before loading? If yes, what procedure?
  *   Do you follow a specific crucible/liner cleaning or replacement procedure?
  *   If you have identified a root cause or corrective action for a similar observation, any details would be highly appreciated.

Our objective is to compare practices across facilities and determine whether this is a material-handling, source/liner, chamber-condition, or process-related phenomenon.

Any suggestions/inputs are highly appreciated.
Thanks in advance!

Regards,
CHANDAN H B
THIN FILMS ENGINEER
CAUTION: This email was NOT sent from an authorized Cal Poly Pomona service. Please review carefully before responding, clicking links, or opening attachments. Report phishing messages using the Outlook app<https://support.microsoft.com/en-us/office/phishing-and-suspicious-behavior-in-outlook-0d882ea5-eedc-4bed-aebc-079ffa1105a3> (mobile, web or desktop) or forward suspicious email to suspectemail at cpp.edu<mailto:suspectemail at cpp.edu>.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20260917/88f40317/attachment.html>