Monolayer Counting objectives

1. Monolayer Countingobjectives Compare results from type 1 and type 2 boxcar smoothing to observe which one is better at counting zero crossings of slopes without generating a lot of false positives. Investigate what triggers false positives to gain insight about how to avoid them.

2. 305ge065 – type 1 Raw data is in red. Blue points indicate when a count would be triggered by the current algorithm. The current algorithm watches the current time and the predicted time of a zero crossing. If a prediction is made for a zero crossing which will occur before the next step the program counts. This plot isn’t perfect because several crossings are missed which would be caught by the backup counter which simply watches the sign of the slope. Note: Raw data in the slope chart refers to the derivative of the type 1 boxcar average not the derivative of the actual raw data.

3. 305ge065 – type 2 Raw data is in red. Blue points indicate when a count would be triggered by the current algorithm. The current algorithm watches the current time and the predicted time of a zero crossing. If a prediction is made for a zero crossing which will occur before the next step the program counts. This plot isn’t perfect because several crossings are missed which would be caught by the backup counter which simply watches the sign of the slope. Note: Raw data in the slope plot refers to the derivative of the type 2 boxcar average.

4. Observations • Type 1 has 23 counts while type 2 has only 19 • Type 1 triggers counts when the data first starts and is not showing real RHEED oscillations, Type 2 does not.

5. 305ge065 – ½ and 1st monolayer The 2nd type picks the crossing to be closer to the actual minimum for the first half monolayer. The 1st type counts the first full monolayer twice (and remember it is already miscounting because of the data before the actual oscillation began. This is a good time to remember that in reality the type 2 will be offset by one data point because it only looks at the smoothed points and the most recent point is never smoothed.

6. 305ge065 – ½ and 1st monolayer This is similar to the last slide but looks at the slope and goes back to the start of the experiment.

7. 305ge065 Predictions – ½ monolayer Actual = 24.626 sec 1st are predictions made by type 1 2nd are predictions made by type 2 Horizon is a 1:1 line for reference Type 2 are crossings given by type 2 Type 1 are crossings given by type 1 Each column is a difference between a type’s prediction and either the actual crossing or the horizon line.

8. 305ge065 Predictions – 1 monolayer Actual = 30.627 sec Each column is a difference between a type’s prediction and either the actual crossing or the horizon line. 1st are predictions made by type 1 2nd are predictions made by type 2 Horizon is a 1:1 line for reference Type 2 are crossings given by type 2 Type 1 are crossings given by type 1

9. 305ge065 – 3/2 and 2nd monolayer Type 1 misses the 3/2 monolayer and counts the 2 monolayer twice; once early and once late. Type 2 seems to hit the crossings close to where they happen.

10. 305ge065 – 3/2 and 2nd monolayer Slope view

11. 305ge065 Predictions – 3/2 monolayer Actual = 37.915 sec 1st are predictions made by type 1 2nd are predictions made by type 2 Horizon is a 1:1 line for reference Type 2 are crossings given by type 2 Type 1 are crossings given by type 1 Each column is a difference between a type’s prediction and either the actual crossing or the horizon line.

12. 305ge065 Predictions – 2 monolayer Actual = 48.715sec 1st are predictions made by type 1 2nd are predictions made by type 2 Horizon is a 1:1 line for reference Type 2 are crossings given by type 2 Type 1 are crossings given by type 1 Each column is a difference between a type’s prediction and either the actual crossing or the horizon line.

13. 305ge065 – 2nd monolayer shoulder Type 2 counts three times for the shoulder (should only count twice) and type 1 counts only one time for the shoulder.

14. 305ge065 – 2nd monolayer shoulder Slope view

15. 305ge065 – 2nd monolayer shoulder No quantitative analysis of the predictions because of the multiple type 2 crossings.

16. 305ge065 – 5/2 and 3 monolayer Type 2 counts the 3 monolayer twice Type 1 counts the 5/2 monolayer and the 3 monolayer once

17. 305ge065 – 5/2 and 3 monolayer Slope view

18. 305ge065 Predictions – 5/2 monolayer Actual = 68.075sec 1st are predictions made by type 1 2nd are predictions made by type 2 Horizon is a 1:1 line for reference Type 2 are crossings given by type 2 Type 1 are crossings given by type 1 Each column is a difference between a type’s prediction and either the actual crossing or the horizon line.

19. 305ge065 Predictions – 3 monolayer Actual = 79.043sec 1st are predictions made by type 1 2nd are predictions made by type 2 Horizon is a 1:1 line for reference Type 2 are crossings given by type 2 Type 1 are crossings given by type 1 Each column is a difference between a type’s prediction and either the actual crossing or the horizon line.

20. 305ge065 – 3rd monolayer shoulder Type 2 counts twice Type 1 counts once

21. 305ge065 – 3rd monolayer shoulder Slope view