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Overflow and electrical breakdown of a tunnel junction

2182 Series Support
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shaoqiming
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Joined: August 11th, 2015, 8:14 pm
Country: United States

Overflow and electrical breakdown of a tunnel junction

Post by shaoqiming » August 11th, 2015, 9:08 pm

Dear Keithley,

We are using 2182A to measure the DC voltage of a magnetic tunnel junction (MTJ). Before we connect the MTJ to the 2182A, 2182A always indicates that it is overflowing (voltage value keeps increasing and then overflow). I tried to short the high and low output, and the value is almost 0, which is correct. But after I keep it open, 2182A charges up and the voltage becomes large. When we connect the MTJ to 2812A, the tunnel junction breaks down. I think the initial voltage may be far larger than the breakdown voltage of MTJ (~ 2V).
Do you think if it is possible? And how could we avoid this issue?

I appreciate your help. Thanks.

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: Overflow and electrical breakdown of a tunnel junction

Post by brian.d.smith » August 12th, 2015, 5:24 am

The input impedance of the instrument is >10G Ohms. If the input is not connected to a load, any capacitance of your cabling will cause the input to charge. That charge is transferred to your device when you connect the 2182A to you device.

You can try this. Connect a parallel resistance across the 2182A input such as 100 ohms or 1000 ohms that can be removed after your device is connected.

You can also try setting the manual range to the highest range (100V) which will decrease the input impedance to 10M ohms. Change the range down manually after you connect your device.

shaoqiming
Posts: 2
Joined: August 11th, 2015, 8:14 pm
Country: United States

Re: Overflow and electrical breakdown of a tunnel junction

Post by shaoqiming » November 27th, 2015, 10:08 am

brian.d.smith wrote:The input impedance of the instrument is >10G Ohms. If the input is not connected to a load, any capacitance of your cabling will cause the input to charge. That charge is transferred to your device when you connect the 2182A to you device.

You can try this. Connect a parallel resistance across the 2182A input such as 100 ohms or 1000 ohms that can be removed after your device is connected.

You can also try setting the manual range to the highest range (100V) which will decrease the input impedance to 10M ohms. Change the range down manually after you connect your device.
I appreciate your fast reply and sorry for late response.
Your suggestions help a lot. I tried both methods you suggested and they work for my measurement.

brian.d.smith
Keithley Applications
Keithley Applications
Posts: 402
Joined: June 10th, 2013, 6:00 am
Country: United States

Re: Overflow and electrical breakdown of a tunnel junction

Post by brian.d.smith » November 30th, 2015, 4:35 am

I am glad to hear that your problem is resolved.

squnafeesa
Posts: 1
Joined: August 15th, 2017, 2:02 am
Country: Oman

Re: Overflow and electrical breakdown of a tunnel junction

Post by squnafeesa » August 15th, 2017, 2:37 am

Hi Keithley Team,
I too use 6221+2182A combination for Magnetic Tunnel Junction study.I tried both methods suggested above.The voltmeter 2182A showing " OVRFLW " after few minutes of switching it on,whatever be the load Resistance,even with cable removed.
Thanks.

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